Well, thanks for the suggestion, but it's certainly not for everyone.
Sometimes my sleep-awake schedule breaks and it's a PITA.
I can lie for hours in a almost complete darkness, counting breaths/sheeps/listening to rain outside/etc and still not falling asleep for a single bit. Melatonin doesn't do much; haven't tried anything else. Then, when it's a day already, nor willpower, nor direct sunlight, nor coffee is not enough to keep me awake for a long time - usually I can't stay until evening. Let me lay for a minute and I'll be asleep even if the sun's shining right onto my closed eyes.
The only way for me to fix my schedule seems to gradually shift sleep times by several hours (i.e. go to sleep at 10:00 [a.m.], then 13:00 then 15:00 and so on) until I'm again falling asleep in the late evening and waking up at morning. Then I'd have to do my best to not break the schedule again, i.e. not fall asleep too early and not stay up for too late.