I try, not always successfully, to keep regular hours and meal times. I'm a bit bipolar, and inspiration can keep me up. If I'm facing a stressful day, I use a check list so I can stop going over the plans. Usually, I try to start the sleep process before exhaustion by shutting down the screen(s), using "warm" lighting, and reading something not exciting. Dark and quiet helps, too.
If I need to sleep, but can't, meditation is a partial substitute and another way to try to fall asleep as well. I count my breaths, from zero to twelve, and try to only think about the "character" of each, like is it prime or not, and how it fits in the set. Sometimes, I have a lot of short dozes - all I notice is that some of my thoughts don't make sense - I'm dreaming! To really get rested, though, I think that 90 minute sessions are the minimum for effective flushing of brain wastes, and it takes at least four a day at that length.
Before electricity, people often slept twice a day, especially in winter, arising for the middle of the night to stoke fires, do chores that needed little light, or just talk. Some hot countries enjoy a siesta.