Light cues us to feel awake, and darkness helps us feel sleepy. This is the backbone of our circadian rhythm, or sleep-wake cycle. We evolved seeing bright sunlight during the day, and only moon and fire at night.
But in our modern world, we spend the day in windowless cubicle mazes, and we spend the night surrounded by screens, LED lights, and ambient light pollution. And what do you know? We drag ourselves through the day and can't seem to fall asleep at night. Our circadian rhythms have gotten mixed up.
To get your circadian rhythm back on track, you need to sleep in absolute, pitch-black darkness. Have you ever stopped to notice if your room is actually dark when you go to sleep? If you live in the country, or in a basement, you might actually have a shot at having a dark bedroom. But if you live in a city, or have a streetlamp out your window, or if you have a digital alarm clock, chances are your room is not all that dark when you sleep. My bedroom gets enough ambient New York City light pollution at night that I could run a successful grow house (NSA, if you're reading this, don't worry. I don't do this—just trying to make a point).
So what can you do?
First, look around your room at night with the lights turned off. If you see anything glowing—a digital clock, a computer, an air conditioner—remove the item from the bedroom or cover the light with duct tape or orange tape. I also encourage you to replace your digital alarm clock with a $10 analog clock, or at least get a digital clock with orange numbers, rather than blue or green (orange light is the least disruptive to the circadian rhythm).
Next, strongly consider installing blackout shades. Before you dismiss this idea outright, just know that it ends up being less intimidating than it sounds. I put this off for years. When I finally dragged myself to Home Depot, it was quick and affordable, and I wished I had done it years ago. If blackout shades are not happening, get a good eye mask. My favorite is the Bucky 40 Blinks eye mask.
Finally, I'm asking you to do something drastic: Make the bedroom a no-phone zone. I guarantee you, your phone is screwing up your sleep. When we keep our phone in the bedroom, it's the last thing we look at before we go to bed (sending a shock of blue light into our brains, cuing us to feel wide awake), and the first thing we look at when we wake up (starting off the day with a tone of stress and obligation). The buzzes and dings wake us imperceptibly throughout the night, making our sleep more superficial and less restorative.
If you use your phone as your alarm clock, no big deal. Go buy an old-fashioned alarm clock. Make this change today.