@academicalnerd There's this funny thing I noticed on myself: When I "explicitly ask myself" in the evening to wake up at a certain time, my body does it almost precisely on spot. I am not going into deeper reasons why that's the case (for me at least), but it works for me since ever (like 80-90% of times). Maybe it's a result of some inner anxiety, or something. Dunno.
Of course this only works when my health is OK-ish, that is, no alcohol and at least so-so not sleep deprived, or dead tired.
My problem is different: if my body decides to wake up at some time, regardless of how long I slept, I'd have a difficulty falling back to sleep. Sometimes meditation helps, but it's difficult nevertheless.
@FailForward
Yeah, I do this too, works most of the time. My goal now is to sleep as much as my body needs, not as much as I want to. Because I want to do stuff, but my body needs to play dead for 8 hours or so :p