The best way to have a good sleep is to stop being anxious and depressed, forget bad things, stay happy, be relaxed at evening, have a good hormonal profile, eat healthy, have a strict circadian discipline, a loving partner and live a nice live in general.

Exercise helps with the relaxed part.

It was like that for me, until it wasn't. I am still weight lifting but my sleep is much worse if I push too much. Sleep issues are simple only until you have them.

Weight lifting in the evenings can do that because you're increasing stress hormone output. Try switching to morning or afternoon workouts.

Running properly is just as tiring as a good weight session.

but it doesn't build muscle the same way, which you'll want as age starts to remove muscle

Maybe, but I just can't sleep after running.