You're not alone. I'm in a fortunate place and I saw mine coming. I've been working out way harder and taking health very seriously (mental + physical). I've met so many booted tech guys these past few months it's wild (dunno your profession). Stay active. See friends. Maybe take a trip you have been wanting to do (but maybe wait until you are ready to enjoy it). Maybe focus on that hobby you've had. But most importantly, don't rush into something completely new, like a side project, an existing one, sure, but maybe not put a bunch of hope into a new one. It will fail when you run out of energy and you will be upset, and realize it wasn't worth it.

For me it's time. There is no one thing that's helping me.

Hope that helps. Always ask for help, chin up. :)