Essentials: Master Your Sleep & Be More Alert When Awake

The most powerful thing that's governing when you want to be asleep and when you want to be awake is light, and in particular, it's governed by sunlight. And I can't emphasize enough how important and how actionable this relationship is between light and when you want to sleep.

It's 50 times less effective to view the sunlight through a window, through a car windshield, or through a side window of a car than it is to just get outside with no sunglasses and view light early in the day.

Viewing sunlight around the time of sunset... prevents some of the bad effects of light in preventing melatonin release later that same night.

The longer you've been awake, the more sensitive your retina and these cells are to light ... If you've been awake for 10, 12, 14 hours, it becomes very easy for even a small amount of light coming from a screen or from an overhead light to trigger the activation of the clock and make you feel like you want to stay up later, make it harder to fall asleep, and disrupt your sleep pattern.

If you're finding that you can't become a day person or a morning person, shifting your light exposure, exercise and food intake to the daytime will help.

If you see light late in the day—and in particular, in the middle of the night—your brain and body, for reasons that now you understand, will think that that's morning light, even though it's not sunlight, because you have this heightened sensitivity, and it will phase delay, it will delay, your clock. It will essentially make you want to get up later and go to sleep later.

If you don't get your cortisol and melatonin rhythms right, there are tremendously broad and bad effects on cardiovascular health, metabolic effects, learning, depression, dementia.

Adenosine is a molecule in our nervous system and body that builds up the longer we are awake ... Adenosine creates a sort of sleep drive or a sleep hunger.