I find that for me not being able to fall asleep is mental thing, not a physical thing. There are thoughts I have where I can feel my brain click and turn on and I’m awake and that is that.
I avoid thinking about things that are interesting. You can only think about one thing at a time, most of the time I just count. Switching between thoughts is not the same as thinking about multiple things at the same time. Focus on the numbers, sometimes try to visualize them on a chalk board if I’m being kept awake by images. Just count. Slow, focused. If my mind drifts off the numbers to another topic, I go back to 1 and start again. It is weird that thinking hard about something not interesting is relaxing.