What helped me the most against my insomnia is simply accepting it. I just stopped fighting to try to sleep. It didn‘t help immediately, but at least the time that I wasn‘t falling asleep was less painful. Over time (several months/years) my insomnia eventually went away.

Years later I listened to an audio book by The psychologist Viktor Frankl, that also helped me relax about the topic.

And of course jogging (without music) or something similar that essentially switches off your brain during day time.