Also alarm clocks, caffeine, unnatural sleep schedules. This site[1] has lots of good information, with this basic (unfortunately impossible for many) recommendation:
"There is only one formula for healthy and refreshing sleep: Go to sleep only when you are very tired. Not earlier. Not later. Wake up naturally without an alarm clock."
"There is only one formula for healthy and refreshing sleep: Go to sleep only when you are very tired. Not earlier. Not later. Wake up naturally without an alarm clock."
[1] https://supermemo.guru/wiki/Science_of_sleep