OK, here’s what you do. 30 minutes before the time you want to go to bed, or an hour, or 3 hours, set a timer for 5 minutes and tell yourself sternly for the five minutes that you’re gonna go to bed when it’s bedtime, you’re really gonna do it, you’re not gonna fuck around this time.* Don’t just say the words, hear yourself saying them. Visualize yourself doing it. Be loud if you have to be. Be animated. Make a scene. (Privately.) Then set a timer to go off at your bedtime. You’ll go to bed.
*If you're dumb, call yourself that. If you kinda smell, say that. Threaten yourself with a bath. (The self-abuse is secondary, though.)