> "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."

I did that for years when I was younger. For me that meant a longer-than-24-hour day which quickly led to being completely nocturnal. Those were dark days, literally and figuratively. I can distinctly remember my first "day" without daylight. It wasn't a nice feeling. I would usually try to correct it when that happened which was like having a 12 hour jet lag.