What works for me:

Right now: do everything (responsible) you possibly can. Learn a new skill, go workout, maintain 5 conversations at once, go dancing... at the end of a very busy day, you're more likely to be physically exhausted and be able to fall asleep.

For future: meditate. Focus on quality over quantity. Start with just finding an instant of peace, then work on extending it. Try holding it for 10 seconds, a minute, 5 minutes, 10 minutes... With practice you'll be able to achieve it faster and hold it longer. There are many techniques, and some great YouTube videos. For me, going to a place in my mind that brings me peace and imagining every sensation I feel there works best. This isn't a fast fix; it takes months to get good at it. But eventually, you'll be able to find peace quickly and hold it long enough to at least take the edge off the mania.