Streetwiseguy said:
How much of it is just in your nature? How can a person control what their brain decides to chew on in the middle of the night?
If you figure it out, let me know.
More than you'd think. Although, in my experience, it's a bit more nuanced than that.
It's training habits, reflexes, and responses the same as you'd train yourself for anything else. There are different methods, techniques, and tricks that work better for different people. It's ultimately all teaching yourself to redirect your thinking.
Almost the same idea as training yourself to look farther ahead down track, look through the turns, and think about setting yourself up two turns ahead, to train yourself out of panic-focusing on hazards and constantly second-guessing imperfect inputs while driving. You're not training your mind to not bounce around a bunch of crazy ideas. You're training yourself not to wrestle with every single new thing your brain pops up with.
Different techniques work better for different people. Professional therapy, meditation, mindfulness practices, and small rituals are all potentially useful tools.
I've done some mindfulness meditation stuff. That helped a lot for a while. Now I have good luck with just putting down electronics a minimum amount of time before I want to sleep, and going through a particular nightly ritual before bed: a quick series of stretches, then reading. Listening to records also helps me a lot too. Specifically records, because it's a ritual that forces me to stop and do one thing slowly and intentionally, then to just sit for 20 minutes and pay attention to one thing.
The more you practice things like that, it's not that the distracting thoughts pop up less, but I react to them differently. It's like, "Oh yeah. That's a distracting thought. Whatever," and then it slips away and I can go back to listening to the music or paying attention to the aromas of my Scotch instead of wrestling with the thought.