Rain was pouring down in New York City as Gretchen Rubin hopped on a city bus and settled in for a long ride, taking the opportunity to enjoy a moment of reflection. Rubin pondered, "What do I want from life, anyway?" Of course, she decided, she wanted to be happy.

But like many of us, Rubin had little idea of what would actually make her happy -- or what happiness meant in the first place. Rubin decided to answer these questions for herself, creating her personal "happiness project" -- an exploration of ancient and modern wisdom about what it means to lead a good life. What started as a personal passion project turned into the 2011 bestselling book and cultural phenomenon, The Happiness Project: Or, Why I Spent A Year Trying To Sing In The Morning, Clean My Closets, Fight Right, Read Aristotle, And Generally Have More Fun.

With her simple questions -- Can we make ourselves happier, and what would that require? -- Rubin joined a conversation that has long dominated the booming self-help industry and the expanding field of positive psychology. Today, happiness is ever-present in our cultural conversation and often at the forefront of our minds. Advice on how to be happy is everywhere: A Google search for "happiness" yields 75 million results, and nearly 40,000 books on or related to the topic are available for purchase on Amazon.com.

While the depth and zeal of our current obsession with being happy may be unprecedented, happiness is an ancient, time-honored pursuit. Aristotle -- one of Rubin's Happiness Project inspirations -- may have been the original (if accidental) self-help guru, interrogating the causes and definitions of happiness at length in his Nicomachean Ethics.

Excerpts of that text have been co-opted by thousands of present-day self-help books, lectures, seminars, blog posts and articles touting the secrets and steps to unlimited happiness. And yet the American happiness industry has come to sell a much different vision of the good life than what Aristotle had in mind.

Whereas Aristotle believed that happiness was the by-product of a life of virtue, we've come to associate happiness with a more vague metric of "feeling good." Rather than thinking in terms of living virtuously, we've come to associate happiness more with the avoidance of pain and pursuit of pleasure, with personal gratification or sensory pleasures.

This shift from being good to feeling good began in the 18th century. Thomas Jefferson's Declaration of Independence -- which identifies the pursuit of happiness as an unalienable right, along with life and liberty -- and the French Revolution both reflected an increasingly popular idea: that happiness is necessary for the health of the individual and society. The rising popularity of utilitarianism also led to a new way of conceptualizing happiness in terms of a pleasure vs. pain.

So why the recent resurgence of interest in happiness? Rubin -- now a happiness guru, the author of two books on the subject, a sought-after public speaker and nationally syndicated columnist -- believes that the combination of unprecedented prosperity and uncertainty about the future are the driving factors causing people to question what really matters to them.

When we're able to provide for our families but face economic and political uncertainty at the same time, Rubin says, we focus on what we can control and what we really want from life.

"On the one hand, people's feelings of insecurity made them focus on happiness," Rubin told The Huffington Post, "but exactly the opposite is also true, which is that if you look in any kind of historical framework, we live in a time of incredible prosperity and security. So that frees people to think about, 'Do I have meaningful relationships? Do I get satisfaction from work? Do I feel like my life is what I want it to be?'"

Happiness has become a core question of our lives. Some psychologists argue that this preoccupation with happiness may actually be making us less happy. Critics have also pointed out that the obsession with happiness may lead some to discount both the presence and the value of the challenging and painful events that are inevitable in our lives -- not to mention making us feel inadequate when we fall short of an ideal happiness.

"A culture that talks about happiness as much as we do is giving the sign that we're concerned about happiness, and I mean concerned in a slightly negative way," said Darrin McMahon, a historian at Florida State University and author of Happiness: A History. "We obsess about happiness, and that may be an indication that we're not actually all that happy."

Happiness Through The Ages

Aristotle defined happiness as a life lived in accordance with virtue, and outlined a philosophy of becoming happy through acting virtuously.

"Men generally agree that the highest good attainable by action is happiness, and identify living well and doing well with happiness," Aristotle wrote.

"For Aristotle, happiness isn't a feeling, but an evaluation of a life lived well," said McMahon. "That begins to shift in a profound way in the 18th century ... people start defining happiness as a feeling, an emotion, as what puts a smile on your face."

With the rise of utilitarian principles in the 1700s, the idea that the individual should maximize pleasure and minimize pain became prevalent in the cultural conversation. The 18th century British economist and founding father of utilitarianism Jeremy Bentham -- who believed that societies and individuals should act in such a way as to promote the "greatest happiness for the greatest number" -- defined happiness in this way, as a pleasure/pain calculus.

As a result of this cultural shift, people were presented with a novel prospect: "They can be happy, and they should be happy," said McMahon.

The idea of happiness was central to some of the 18th century's defining movements. Rousseau's Social Contract posited that the rules of society must be created with humanity's happiness in mind. And of course, in the United States, the Declaration of Independence positioned happiness (or at least its pursuit) as an "unalienable right" of the individual.

The legacy of those Enlightenment principles still informs our conception of happiness, even as happiness itself has taken on functions more often associated with religion. According to McMahon, happiness, rather than service to God or spiritual transcendence, has come to be seen as the ultimate aim of life in many cultures.

"[Happiness] is really the last great organizing principle of a life," McMahon said. "We no longer live our lives according to beauty or honor or virtue. We want to live in order to be happy."

Like Rubin, McMahon associates the rising concern and preoccupation with happiness with two main factors: declining religious belief and economic prosperity.

"The key question then becomes why," McMahon explained. "To really be concerned about your happiness is a total luxury: It only happens when everything else is taken care of. To care about happiness in a really sustained, neurotic way ... is on one level a sign of our prosperity."

This shift in priorities is even reflected in how we've started to quantify national success, as gross national happiness has the attention of leaders alongside gross national product. According to the largest global happiness survey, the United Nations World Happiness Report, the world is becoming a happier place. World well-being is on the rise, according to the UN, with countries where happiness is up outnumbering those where it's down.

"It's time we admitted that there's more to life than money, and it's time we focused not just on GDP, but on GWB -- general well-being," said British Prime Minister David Cameron at a Google Zeitgeist Europe conference in 2006. "Well-being can't be measured by money or traded in markets. It's about the beauty of our surroundings, the quality of our culture and, above all, the strength of our relationships."

The Modern Science Of Happiness

Research in positive psychology has legitimized the study of happiness and brought it to the forefront of the cultural dialogue, simultaneously boosting the prominence of happiness studies and complicating how the term is defined.

Psychologists and neuroscientists have arrived at insights into humanity's inherent capacity for happiness -- what's known as the "happiness set point" -- as well as one's potential to be more or less happy.

"As a rough generalization, about a third of the factors that determine outcomes of well-being are genetic or biological," cognitive psychologist Rick Hanson, author of Hardwiring Happiness, told HuffPost. "That leaves abut two-thirds that are based on the environment around us and what we do inside ourselves."

The problem is that the brain is attracted more to negative experiences than positive ones. In Hanson's analogy, the brain is like Teflon for positive experiences and Velcro for negative ones. His research has found that the simple secret to boosting our happiness levels is to maximize life's everyday simple pleasures and small joys, which we can do by lingering on positive moments and finding small ways to build more joy into our lives.

"If we train ourselves increasingly to look for the positive, we have trained our brain in terms of what it's primed to see and what it's scanning for," said Hanson.

Having positive experiences more often tends to increase flows of dopamine, the chemical that tracks rewards, in the brain, which builds out more receptors for dopamine, and over time makes us more sensitive to reward, says Hanson.

Research has also pinpointed certain scientifically backed happiness boosters: Exercise, sleep, sex, playing with animals, taking vacations and spending time outdoors are simple things that almost anyone can do to boost a sense of well-being. As a number of studies have shown -- including the Harvard-Grant Study, a 75-year longitudinal investigation into what accounts for a fulfilling life -- strong relationships are consistently the strongest predictor of happiness.

The Harvard-Grant study's director, George Vaillant, concluded that there are two pillars of happiness. "One is love," he said. "The other is finding a way of coping with life that does not push love away."

Running On The Hedonic Treadmill

In the pursuit of pleasure and joy, people tend to fall into the trap of running on the so-called hedonic treadmill -- chasing after pleasures and external recognition that they believe will bring happiness, rather than finding more pleasure in the experiences they're already having.

According to the treadmill theory, outlined in a 2006 paper by Ed Diener, Richard E. Lucas and Christie Napa Scollon, good or bad things temporarily affect our happiness levels, but when those experiences come to an end, we quickly return to neutral. In a consumer culture, it's easy to see how an obsession with happiness can amplify a hedonic treadmill scenario, in which one is constantly looking outside the self for the next quick fix to boost happiness.

"We keep ratcheting up what is luxury and what is pleasure, and yet we also fall back to a kind of baseline," said McMahon. "A market economy operates on that, but it's not necessarily designed to make us happier... In some ways this will always be a losing proposition."

A number of industries, particularly self-help, benefit from this arrangement. In the last several decades, a growing desire to buy happiness has made self-help into money-making mega-genre. Meanwhile, positive psychology has become a staple of the corporate world, promising to make employees happier, and therefore more productive and more creative.

"There are snake oil salesmen in the business world who are making massive amounts of money by selling positive psychology to corporations as a way to organize workforces," said McMahon. "But there's not a whole lot of science behind what they're claiming, at times."

McMahon also questions the motives driving the corporate positive psychology movement.

"It's good and bad -- they want you to flourish, but they also want to get more out of you," he said. "These psychological techniques are being used to increase productivity, and that's not a bad thing, but sometimes you wonder what the ultimate goal is. Is it profit maximization, or having flourishing people?"

The trouble lies not in the field of positive psychology or in the research coming out of it -- but in the proposition that happiness is something that can be easily bought or crafted.

"There's a certain tendency in our culture to want to graft some kind of happiness onto an existing structure," Hanson said. "If you just fill in the blank -- get this car, find the right shade of lipstick, go on vacation in Mexico, lose those five pounds -- suddenly you'll be happier and have the fulfillment you want in life ... Let's be clear: The main happiness industry in America is the advertising industry."

A New Disease Of Western Societies

One risk inherent in our obsession with the pursuit of happiness is that we will begin to fear or devalue painful, negative emotions and challenging experiences.

For Australian social researcher Hugh Mackay, the notion that individuals should do everything for the sake of happiness is a dangerous one. In his book The Good Life, Mackay argues that this philosophy has led to a new disease among Western societies: "fear of sadness."

Mackay explains that it's wholeness, not happiness, that we should be after:

It's a really odd thing that we're now seeing people saying, "Write down three things that made you happy today before you go to sleep," and "Cheer up" and "Happiness is our birthright," and so on. We're kind of teaching our kids that happiness is the default position -- it's rubbish. Wholeness is what we ought to be striving for and part of that is sadness, disappointment, frustration, failure; all of those things which make us who we are. Happiness and victory and fulfillment are nice little things that also happen to us, but they don't teach us much ... I'd like just for a year to have a moratorium on the word "happiness" and to replace it with the word "wholeness." Ask yourself "Is this contributing to my wholeness?" and if you're having a bad day, it is.

But positive psychology itself isn't about the denial of negative experiences -- what Martin Seligman, the father of positive psychology, calls "happyology" -- but also encompasses qualities like resilience and persistence, which help us to grow and thrive through negative experiences.

"[Positive psychologists] are actually interested in what makes a full, flourishing life," McMahon explained.

Hanson agreed, adding that taking a negative stance towards negative experiences just creates even more negativity. "Sorrow tenderizes the heart," Hanson said. "Attending to the suffering of one's self and others has dignity to it -- a nobility even -- and it's important to do, particularly in our culture that always wants to 'fix it fast.'"

The Mindful Happiness Revolution

The search for quick fixes is likely to leave one stuck on the treadmill -- but mindfulness may be the remedy to a tendency to look for easy solutions.

"If a person skillfully does inner practices and gradually becomes more mindful and more caring ... they're not going to fall into the pitfalls of chasing after every little pleasure they can find," Hanson said.

This inner practice is key -- and it's something to which some are starting to pay more attention. The so-called mindful revolution -- "a meeting of minds between positive psychology and Buddhism," as McMahon describes it -- may very well be a turning point in how the culture looks at happiness.

Mindfulness is not a panacea, but the practice does have science on its side when it comes to boosting well-being. Mindfulness practice has been linked with emotional stability, reduced stress, depression and anxiety, and improved mental clarity. It also could aid individuals in seeing themselves more clearly -- free from positive or negative biases -- according to a 2013 University of Utah study.

"People who reported higher levels of mindfulness described better control over their emotions and behaviors during the day," University of Utah researcher Holly Rau said in a statement. "In addition, higher mindfulness was associated with lower activation at bedtime, which could have benefits for sleep quality and future ability to manage stress."

The research supports something that Rubin has found in her own exploration of happiness: That self-knowledge is the bedrock of joy and fulfillment.

"Part of it is thinking, 'Well, what do you want?'" Rubin said, "and not just accepting some ready-made definition. It's easy to assume that you want something, and then you lose track of what's true for you ... So much of it is being aware of what you're doing ... and once you know, you can direct it."

Mindfulness, which has been shown to boost compassion and may even improve relationship quality, may also bring us back to a more Aristotelian notion of happiness as a life in which we are good to others.