January is the month of broken resolutions. The gyms are packed for a week, Jenny Craig is full of new recruits and houses are cleaned for the first time in ages. We pledge to finally become the person we want to be: svelte, neat and punctual.

Alas, it doesn't take long before the stairmasters are once again sitting empty and those same dirty T-shirts are piling up at the back of the closet. We start binging on pizza and beer – sorry, Jenny – and forget about that pledge to become a kinder, gentler person. Human habits, in other words, are stubborn things, which helps explain why 88 percent of all resolutions end in failure, according to a 2007 survey of over 3,000 people conducted by the British psychologist Richard Wiseman.

The reason our resolutions end in such dismal fashion returns us to the single most important fact about human willpower – it's incredibly feeble. Consider this experiment, led by Baba Shiv, a behavioral economist at Stanford University. He recruited several dozen undergraduates and divided them into two groups. One group was given a two-digit number to remember, while the second group was given a seven-digit number. Then, they were told to walk down the hall, where they were presented with two different snack options: a slice of chocolate cake or a bowl of fruit salad.

Here's where the results get weird. The students with seven digits to remember were nearly twice as likely to choose the cake as students given two digits. The reason, according to Shiv, is that all those extra numbers took up valuable space in the brain – they were a "cognitive load" – making it that much harder to resist a decadent dessert. In other words, willpower is so weak, and the conscious mind is so overtaxed, that all it takes is five extra bits of information before it becomes impossible for the brain to resist a piece of cake.

This helps explain why, after a long day at the office, we're more likely to indulge in a pint of Häagen-Dazs. (In fact, one study by researchers at the University of Michigan found that just walking down a crowded city street was enough to reduce measures of self-control.) A tired brain, preoccupied with its problems and run down by the world, is going to struggle to resist what it wants, even when what it wants isn't what we need.

The problem is only compounded by studies showing that the very act of dieting can make it even harder to resist temptation. In a 2007 experiment, Roy Baumeister – the influential psychologist behind the ego-depletion model of willpower and co-author of the interesting Willpower – gave students an arduous attention task, in which they had to watch a boring video while ignoring words at the bottom of the screen. Then, the students drank a glass of lemonade. Half of the students got lemonade with real sugar, while the other half got a drink made with Splenda. On a series of subsequent tests of self-control, the group given fake sugar performed consistently worse. The literal lack of sugar in their prefrontal cortex, that neural "muscle" behind willpower, made it even harder to not give in.

Is there a way out of this willpower trap? Are there secret exercises that can make it easier to stick with our new year resolutions? Not really. Baumeister has found that getting people to focus on incremental improvements, such as the posture of the back, can build up levels of self-control, just as doing bicep curls can strength the upper arm. Nevertheless, it's not clear that most people even have the discipline to focus on their posture for an extended period, or that these willpower gains will last over the long term.

But there is a neat way to circumvent the intrinsic weakness of the will, which helps explain why some people have a much easier time sticking to their diet and getting to the gym. A fascinating new paper, led by an all-star team of willpower researchers including Wilhelm Hofmann, Baumeister and Kathleen Vohs, gave 205 participants in Würzburg, Germany a specially designed smartphone. For seven days, the subjects were pinged seven times a day and asked to report whether they were experiencing a strong desire. The participants were asked to describe their nature of their desire, how strongly it was felt, and whether it caused an "internal conflict," suggesting that this was a desire they were attempting to resist. If a conflict existed, the subjects were asked to describe their ensuing success: Did they manage to not eat the ice cream? The researchers suggest that this is the first time experience-sampling methods have been used to "map the course of desire and self-control in everyday life."

Christian Jarrett, at the excellent BPS Research Digest, summarizes the results:

The participants were experiencing a desire on about half the times they were beeped. Most often (28 per cent) this was hunger. Other common urges were related to: sleep (10 per cent), thirst (9 per cent), media use (8 per cent), social contact (7 per cent), sex (5 per cent), and coffee (3 per cent). About half of these desires were described as causing internal conflict, and an attempt was made to actively resist about 40 per cent of them. Desires that caused conflict were more likely to prompt an attempt at active self-constraint. Such resistance was often effective. In the absence of resistance, 70 per cent of desires were consummated; with resistance this fell to 17 per cent.

But not everyone was equally successful at resisting the psychological conflict triggered by unwanted wants. According to the survey data, people with higher levels of self-control had just as many desires, but they were less likely to feel that their desires were dangerous. Their desires also tended to be less intense, and thus required less inner strength to resist.

These findings are incredibly revealing, as they document the banal secret of willpower. It's not that these people have immaculate wills, able to stare down tempting calories. Instead, they are able to intelligently steer clear of situations that trigger problematic desires. They don't resist temptation – they avoid it entirely. While unsuccessful dieters try to not eat the ice cream in their freezer, thus quickly exhausting their limited willpower resources, those high in self-control refuse to even walk down the ice cream aisle in the supermarket.

This experience-sampling study neatly confirms the influential work of Walter Mischel, which I wrote about in the New Yorker. In the late 1960s, the Mischel began a simple experiment with four-year-old children. He invited the kids into a tiny room, containing a desk and a chair, and asked them to pick a treat from a tray of marshmallows, cookies, and pretzel sticks. Mischel then made the four-year-olds an offer: They could either eat one treat right away or, if they were willing to wait while he stepped out for a few minutes, they could have two treats when he returned. Not surprisingly, nearly every kid chose to wait.

At the time, psychologists assumed that the ability to delay gratification — to get that second marshmallow or cookie — depended on willpower. Some people simply had more willpower than others, which allowed them to resist tempting sweets and save money for retirement.

However, after watching hundreds of kids participate in the marshmallow experiment, Mischel concluded that this standard model was wrong. He came to realize that willpower was inherently weak, and that children that tried to outlast the treat — gritting their teeth in the face of temptation — soon lost the battle, often within 30 seconds.

Instead, Mischel discovered something interesting when he studied the tiny percentage of kids who could successfully wait for the second treat. Without exception, these "high delayers" all relied on the same mental strategy: they found a way to keep themselves from thinking about the treat, directing their gaze away from the yummy marshmallow. Some covered their eyes or played hide-and-seek underneath the desk. Others sang songs, or repeatedly tied their shoelaces, or pretended to take a nap. Their desire wasn't defeated — it was merely forgotten.

Mischel refers to this skill as the "strategic allocation of attention," and he argues that it's the skill underlying self-control. Too often, we assume that willpower is about having strong moral fiber or gritting our teeth and staring down the treat. But that's wrong — willpower is really about properly directing the spotlight of attention, learning how to control that short list of thoughts in working memory. It's about realizing that if we're thinking about the marshmallow we're going to eat it, which is why we need to look away.

The same lesson applies to adults. Although we might not be able to resist the delicious temptations of the world – they are simply too tempting – we can outsmart them, finding ways to avoid that internal conflict in the first place. The only way to boost willpower is to recognize the inherent weakness of the will.

Image: lucidtech/Flickr/CC-licensed