Seconding lots of things.
If I don’t want to go to bed, I’m not going to sleep—unless I’m absolutely physically exhausted, which isn’t often. So getting my head ready for bed is key for me.
Something I find really helpful is to set the table for the next morning. I pick one of the next day’s tasks and do some preparation: write up a plan, set up a checklist, get materials ready, etc. If “Ugh, tomorrow!” pops into my head, I have “X is done, Y is ready to go.”
As a general rule I stay firmly disconnected from any social media drip feeds—Hey, an endless merry-go-round of anxiety-laden stimuli! Unsubscribe!—and at night I’m freakin’ vigilant about it. Discussion forums like this one (minus P&R) and some lightweight, well-moderated subreddits are all I’ll expose myself too.
Other distractions are welcome, though. I’ve mentioned it before in a similar thread, but CalTech physicist David Goodstein’s The Mechanical Universe series is a real tonic. Aaron Fletcher’s narration, especially, is super relaxing. “Narcoleptically soothing,” to quote myself, and wonderful to doze off to. Arrested Development makes for surprisingly relaxing background noise, too. No laugh track, and very few explosions.
Plus all the usual stuff: Regular meals, at least some physical activity during the day, no caffeine after lunch, no sugary snacks in the evening. The “no evening sweets” is pretty important, I now realize—which sucks, because a nice sugar rush and giggling at goofy shit is one of my favorite things. But it’ll reliably tack on an extra hour or two of wakefulness.