“Many people will tell you that they can’t nap. The one thing I learned from a single yoga class I took many years ago was to slow down my breathing. I just keep breathing slowly in and out and don’t think I must fall asleep. Instead, I think things like, Sleepytime! and just focus on my breathing. I also make sure it’s dark in the room, or I cover my eyes with one of those airplane sleep masks. Also, I set my phone alarm for twenty-one minutes because turning a short power nap into a longer sleep can leave you groggy. This amount of time gives me what’s basically a cognitive reboot.”

Amy Alkon, syndicated columnist and catnap queen

You may be surprised to learn that simply being awake creates toxic products in your brain. During sleep, your cells shrink, causing a striking increase in the space between your cells. This is equivalent to turning on a faucet—it allows fluid to wash past and push the toxins out.This nightly housecleaning is part of what keeps your brain healthy. When you get too little sleep, the buildup of these toxic products is believed to explain why you can’t think very clearly. (Too little sleep is affiliated with conditions ranging from Alzheimer’s to depression—prolonged sleeplessness is lethal.)

Studies have shown that sleep is a vital part of memory and learning. Part of what this special sleep-time tidying does is erase trivial aspects of memories and simultaneously strengthen areas of importance. During sleep, your brain also rehearses some of the tougher parts of whatever you are trying to learn going over and over neural patterns to deepen and strengthen them.

Finally, sleep has been shown to make a remarkable difference in people’s ability to figure out difficult problems and to find meaning and understanding in what they are learning. It’s as if the complete deactivation of the conscious “you” in the prefrontal cortex helps other areas of the brain start talking more easily to one another, allowing them to put together the neural solution to your problem as you sleep.(Of course, you must plant the seed for your diffuse mode by first doing focused-mode work.) It seems that if you go over the material right before taking a nap or going to sleep for the evening, you have an increased chance of dreaming about it. If you go even further and set it in mind that you want to dream about the material, it seems to improve your chances of dreaming about it still further. Dreaming about what you are studying can substantially enhance your ability to understand—it somehow consolidates your memories into easier to-grasp chunks.

If you’re tired, it’s often best to just go to sleep and get up a little earlier the next day, so your reading is done with a better-rested brain. Experienced learners will attest to the fact that reading for one hour with a well-rested brain is better than reading for three hours with a tired brain. A sleep deprived brain simply can’t make the usual connections you make during normal thinking processes. Going without sleep the night before an examination can mean that even if you are perfectly prepared, your mind is simply unable to function properly, so you do poorly on the test.