As a night owl, I abandoned the consistent bedtime approach and went with a pure consistent waketime. The approach that worked for me was having the same wake time, irrespective of time of year, light levels, or tiredness. There are some days when I'm a zombie because I messed up and stayed up too late, but I treat that as a negative reinforcement learning.

The second step was to immediately get out of bed. No matter how warm it was, or how tired I am, no matter how much my brain protested. I moved my alarm to the other side of the room to facilitate this.

What made it stick for me was giving myself permission to be sleepy after the alarm, but not be sleepy in my bed. Many days I stop my alarm, and immediately go to the couch and give my brain some time to boot up before even going to the bathroom or having breakfast

It might be worth saying I _only_ sleep in bed (no reading, no phone, only sleep) and I make sure to _never_ sleep on the couch