Light is the primary cue for our circadian rhythm (sleep-wake cycle). On the proverbial Savannah, this system was foolproof—after sunset, the only light you could see was fire and moonlight. Modern human life is an entirely different story—we spend our days sitting in windowless cubicle mazes, and then the evening is a Technicolor light show of phone, tablet, TV, and laptop screens, on a backdrop of overhead lighting and ambient light pollution outside our windows. Our body misses the cue that it's nighttime and we should feel sleepy. Get strategic to create Savannah light conditions in modern life.
Here's how: Get bright light during the day. Open your blinds as soon as you wake up, and be sure to spend at least some time every day outside in broad daylight.
And experience darkness at night. Dim the lights in your home after sunset, finish the night with a candlelit bath or by reading a paper book in bed by dim lighting. Set your phone on night shift mode and download f.lux on your computer to make the screens dimmer and less blue at night. If you're going to work on the computer, watch TV, or look at the phone at night, consider wearing glasses to block the circadian-disrupting blue light.
As thoroughly discussed above, don't bring the phone into the bedroom. In fact, try to get all electronics out of the bedroom. If your room isn't completely dark once you've turned out the lights, wear an eye mask to sleep or consider getting blackout shades (this ends up being less of an ordeal than it sounds). Finally, if you wake up in the middle of the night, try not to let your eyes "see" any light. You can install an orange night light in the bathroom and do the squinting shuffle, keeping your eyes mostly closed when you go to pee.