I'll bet you're not getting enough sleep. Honestly, I'm kind of cheating — it's a pretty safe bet.

From Why We Sleep:

Two-thirds of adults throughout all developed nations fail to obtain the recommended eight hours of nightly sleep. [Why We Sleep]

And that's bad. Really bad.

Routinely sleeping less than six or seven hours a night demolishes your immune system, more than doubling your risk of cancer. Insufficient sleep is a key lifestyle factor determining whether or not you will develop Alzheimer's disease. Inadequate sleep — even moderate reductions for just one week — disrupts blood sugar levels so profoundly that you would be classified as pre-diabetic. Short sleeping increases the likelihood of your coronary arteries becoming blocked and brittle, setting you on a path toward cardiovascular disease, stroke, and congestive heart failure. Fitting Charlotte Brontë's prophetic wisdom that "a ruffled mind makes a restless pillow," sleep disruption further contributes to all major psychiatric conditions, including depression, anxiety, and suicidality. [Why We Sleep]

So if you're fond of saying, "I'll sleep when I'm dead," well, that may be happening a lot faster than you anticipated.

But I know: You're fine. You don't feel tired. Or you have "taught" yourself to get by on less sleep. Or you have mutant powers. Nope. The truth is you're too tired to realize how tired you are. You're like a drunk shouting, "GIMME THE KEYS! I CAN DRIVE! I'M FINE!"

When participants were asked about their subjective sense of how impaired they were, they consistently underestimated their degree of performance disability. [Why We Sleep]

Which is probably why "... vehicular accidents caused by drowsy driving exceed those caused by alcohol and drugs combined."

You need eight hours. The National Sleep Foundation and the Centers for Disease Control and Prevention both recommend seven to nine hours — but after 10 days of seven hours, your brain is mush whether you realize it or not. So get eight.

After being awake for 19 hours, people who were sleep-deprived were as cognitively impaired as those who were legally drunk. After 16 hours of being awake, the brain begins to fail. Humans need more than seven hours of sleep each night to maintain cognitive performance. After 10 days of just seven hours of sleep, the brain is as dysfunctional as it would be after going without sleep for 24 hours. [Why We Sleep]

Let's not forget: Sleep deprivation is routinely used as a torture method. And we do this to ourselves. Voluntarily.

If two-thirds of people have this problem then we need some real answers from a real expert. Matthew Walker is a professor of neuroscience and psychology at UC Berkeley, the director of its Sleep and Neuroimaging Lab, and a former professor of psychiatry at Harvard University. He's been a sleep consultant for the NBA, the NFL, Pixar, and a bunch of other places your mom would be really impressed by.

His New York Times bestselling book is Why We Sleep: Unlocking the Power of Sleep and Dreams.

We're gonna explode some myths, review the science, and get some great tips on how to sleep better — along with the best way to implement them.

So why do we need sleep anyway?

On the surface, from an evolutionary perspective, sleep makes absolutely zero sense. You can't gather food, find a mate, socialize, or do anything useful while you're out cold. And you're vulnerable to predators.

Yet every animal that has a lifespan of more than a few days sleeps or performs a sleep-like activity. So obviously something pretty darn important is going on. Actually, a lot of important stuff. Sleep is essential for memory and skill development. Cheat yourself on zzz's and learning drops as much as 40 percent. Yeah, that's the difference between an A+ and an F.

When we compared the effectiveness of learning between the two groups, the result was clear: There was a 40 percent deficit in the ability of the sleep-deprived group to cram new facts into the brain (i.e., to make new memories), relative to the group that obtained a full night of sleep. [Why We Sleep]

Sleep is also a built-in therapist, emotionally working out the issues you're dealing with while you're out cold.

REM-sleep dreaming offers a form of overnight therapy. That is, REM-sleep dreaming takes the painful sting out of difficult, even traumatic, emotional episodes you have experienced during the day, offering emotional resolution when you awake the next morning. [Why We Sleep]

That's not too shocking — we've all been moody after a night of little rest. But what you probably don't know is that sleep also helps you deal with the emotions of others. Less slumber means less emotional intelligence.

By removing REM sleep, we had, quite literally, removed participants' levelheaded ability to read the social world around them. [Why We Sleep]

Nobody has ever told you to "stay awake on a problem." And there's a good reason that "sleep on it" is a phrase that exists not only in English, but in numerous languages. Next time your Swahili-speaking friend needs to come up with a creative solution to a tricky challenge, tell them to "kulala juu ya tatizo."

Things were very different for those participants who had obtained a full night of sleep — one dressed with late-morning, REM-rich slumber. Almost 60 percent returned and had the "ah-ha!" moment of spotting the hidden cheat — which is a threefold difference in creative solution insight afforded by sleep. [Why We Sleep]

And from a health perspective, sleep is the after-hours cleaning crew. You make quite a mess in your gray matter with all that thinking you do all day. Without the janitor to sweep up those amyloid dust bunnies you have a much higher chance of developing Alzheimer's.

Without sufficient sleep, amyloid plaques build up in the brain, especially in deep-sleep-generating regions, attacking and degrading them. Getting too little sleep across the adult life span will significantly raise your risk of developing Alzheimer's disease. [Why We Sleep]

And downtime makes you sexy. Yeah, research shows "beauty sleep" is real.

Alrighty: Sleep-deprived bad. Lots-of-sleep good. So if you're only going to do one thing to improve your nightly slumber, what should it be?

Have a consistent sleep schedule

Go to bed at the same time every night. Wake up at the same time every day. It's crucial.

If you can only adhere to one of these each and every day, make it: going to bed and waking up at the same time of day no matter what. [Why We Sleep]

Don't just set an alarm to wake up — set an alarm for bedtime. Build yourself a good pre-sleep routine where you wind down at the same time every night. And if you can get someone to read you a bedtime story, all the better.

You're consistent and ritualized. Great. So let's talk about that thing you hear mentioned constantly: blue light. How your smartphone and iPad screens are teaming up to turn you into an insomniac. Thing is, that's only half the story.

"Blue" light isn't the only problem

All light is bad. Blue is just worse.

Even a hint of dim light — 8 to 10 lux — has been shown to delay the release of nighttime melatonin in humans. The feeblest of bedside lamps pumps out twice as much: anywhere from 20 to 80 lux. A subtly lit living room, where most people reside in the hours before bed, will hum at around 200 lux. Despite being just 1 to 2 percent of the strength of daylight, this ambient level of incandescent home lighting can have 50 percent of the melatonin-suppressing influence within the brain. [Why We Sleep]

That sleep hormone melatonin doesn't just immediately flood your system when you flip the light switch off. It takes time. So dim the lights long before you're ready to hit the sack. And make sure your bedroom is darker than an H.P. Lovecraft story when it's finally time to sleep.

Now everybody knows dark is important when it comes to sleep. But there's a second melatonin trigger that most people don't pay enough attention to.

Be cool

Ever try to sleep when it's too hot? It's not just icky and uncomfortable, but it's also telling your brain that it's not bedtime.

Your nocturnal melatonin levels are therefore controlled not only by the loss of daylight at dusk, but also the drop in temperature that coincides with the setting sun. A bedroom temperature of around 65 degrees Fahrenheit is ideal for the sleep of most people, assuming standard bedding and clothing. [Why We Sleep]

Your body wants its core temperature low when you sleep. So it's gotta dump all that heat you're producing. And this is why you often see people's feet or arms sticking out from under the covers: unconscious heat regulation.

For super sleep, take a hot bath before bed. It doesn't just relax you; it dilates blood vessels, allowing your body to ditch all that extra core warmth. This can boost NREM sleep by up to 15 percent.

When you get out of the bath, those dilated blood vessels on the surface quickly help radiate out inner heat, and your core body temperature plummets. Consequently, you fall asleep more quickly because your core is colder. Hot baths prior to bed can also induce 10 to 15 percent more deep NREM sleep in healthy adults. [Why We Sleep]

Exercise definitely improves sleep but you don't want to do it within three hours of bedtime because — guess what? It raises your core temperature.

I'm guessing you know that drinking a latte and a Red Bull before bed is not a great idea. And you probably heard booze isn't a genius move here either. But there's more to it than that.

No coffee, no booze ... and no sleeping pills

If you want the best sleep possible, you should only use caffeine in the morning or early afternoon.

Caffeine has an average half-life of five to seven hours. Let's say that you have a cup of coffee after your evening dinner, around 7:30 p.m. This means that by 1:30 a.m., 50 percent of that caffeine may still be active and circulating throughout your brain tissue. [Why We Sleep]

And decaf isn't really decaf. It actually contains 15 to 30 percent of the caffeine of a regular cup of coffee. So if you drink three or four cups of decaf after dinner, well, don't be surprised if you're staring at the ceiling at 2 a.m. (To learn more about the science of coffee, click here.)

And, no, alcohol doesn't help you sleep. What it does is actually more akin to anesthesia, which is not "real" sleep. And because it's not the real deal, your brain can't do its memory consolidation work properly.

Those who had their sleep laced with alcohol on the first night after learning suffered what can conservatively be described as partial amnesia seven days later, forgetting more than 50 percent of all that original knowledge. [Why We Sleep]

And sleeping pills affect the same receptors in your brain as alcohol. So you get the same results — except their effects on memory are even worse.

No past or current sleeping medications on the legal (or illegal) market induce natural sleep. [Why We Sleep]

Oh, and there's one other teensy-weensy little problem with sleeping pills ... They don't actually work.

A recent team of leading medical doctors and researchers examined all published studies to date on newer forms of sedative sleeping pills that most people take. They considered 65 separate drug-placebo studies, encompassing almost 4,500 individuals. Overall, participants subjectively felt they fell asleep faster and slept more soundly with fewer awakenings, relative to the placebo. But that's not what the actual sleep recordings showed. There was no difference in how soundly the individuals slept. Both the placebo and the sleeping pills reduced the time it took people to fall asleep (between 10 and 30 minutes), but the change was not statistically different between the two. In other words, there was no objective benefit of these sleeping pills beyond that which a placebo offered. [Why We Sleep]

I'm sure this is going to get me hate mail from Ambien lovers. Emails they won't remember sending, that is.

So what if all of the above isn't cutting it? What if you have stone cold chronic insomnia? What's the cutting edge front-line treatment for the most serious of sleep issues?

To sleep more ... sleep less

If you're only able to sleep six hours a night, then restrict yourself to five. You'll feel like poop the next day and crash hard. But then only let yourself sleep 5 hours and 15 minutes. Now you feel like double poop and will be out before your head hits the pillow. So go to 5 hours and 30 minutes ... And as long as you meet your designated quota, incrementally increase the amount of sleep you allow yourself. No naps.

You'll be a zombie for a while but this is actually a core part of what is now quickly becoming the first-line treatment for chronic insomnia: CBT-I. The application of cognitive behavioral therapy to sleep issues.

One of the more paradoxical CBT-I methods used to help insomniacs sleep is to restrict their time spent in bed, perhaps even to just six hours of sleep or less to begin with. By keeping patients awake for longer, we build up a strong sleep pressure — a greater abundance of adenosine. Under this heavier weight of sleep pressure, patients fall asleep faster, and achieve a more stable, solid form of sleep across the night. In this way, a patient can regain their psychological confidence in being able to self-generate and sustain healthy, rapid, and sound sleep, night after night: something that has eluded them for months, if not years. Upon reestablishing a patient's confidence in this regard, time in bed is gradually increased. [Why We Sleep]

Okay, hopefully that wasn't too exhausting. (Or maybe it's good that it was?) Let's round everything up.

Sum up

Here's how to sleep better:

Have a consistent sleep schedule : Yes, that includes weekends. Yes, I understand that you hate me now.

: Yes, that includes weekends. Yes, I understand that you hate me now. "Blue" light isn't the only problem : Dim the lights in the evening. Set the mood. (Barry White music optional.)

: Dim the lights in the evening. Set the mood. (Barry White music optional.) Be cool : People stick their feet out from under the covers because it's good science.

: People stick their feet out from under the covers because it's good science. No coffee, no booze ... and no sleeping pills : And while I'm ruining everything and being a total buzzkill let me add: There is no Santa Claus.

: And while I'm ruining everything and being a total buzzkill let me add: There is no Santa Claus. To sleep more ... sleep less: Don't think of it as CBT; look at it as getting revenge on your brain for not letting you sleep.

What's the question you definitely want to ask your doctor before your next procedure?

"How much sleep did you get last night?"

The amount of zzz's you get certainly affects your life. But don't forget that how much sleep other people get can affect your life too. Or end it. After a 30-hour shift, residents make 460 percent more errors.

But hopefully you won't be seeing a doctor anytime soon, because you'll be in tip-top shape due to all that glorious shut-eye you're getting.

And this is the one post where if you fell asleep while reading it, well, I'm not offended.

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