Two systems decide when you sleep

Only two, and almost everything that goes wrong goes wrong in one of them.

The first is sleep drive. It builds the whole time you are awake, like hunger. The longer you have been up, and the less you have slept recently, the stronger the pull.

The second is your body clock. It opens a window in which sleep is easy and shuts it again, and outside that window sleep is hard no matter how tired you are. This is why you can be exhausted at four in the afternoon and wide awake at eleven at night.

They are not the same thing and they need different handling. Most sleep advice mashes them together, which is why so much of it feels like it was written for somebody else.