[alistairSH]

Expanding on this post a little bit, because "just go outside" alone isn't particularly helpful...

Find a local park (wooded, not just ball fields). Go for a walk. It doesn't have to long or strenuous - just being outside, in the relative quiet, can be profoundly relaxing.

Maybe you'll find the outdoors isn't your thing, but as far as finding a hobby goes, spending time outdoors in nature is about as low investment as it gets.

Or, if you prefer something a bit more aligned with programming/tech, maybe find a maker club and get into 3d printing, or woodwork, or some similar hobby. These aren't my thing, but I have several programmer friends who love to build stuff - some restore old motorcycles, some do the maker thing, and some ended up with woodshops in the their basements/garages.