[rsanek]

So funny to see the recommendation here (track bedtime/wake-time, compute your average cycle length, predict the next bedtime from it, and don't deviate in either direction) be similar to how spaced repetition is typically sold to people: high expectations from users, no affordances for flexibility. These kinds of systems are just not realistic unless you are willing to be a loner that can never deviate from their routine.

I do agree that caffeine, alcohol, nicotine, sleeping pills, and (as much as we can) alarm clocks are all things to stay away from.