I agree with many here about finding some sort of exercise, it's especially beneficial as we age. Cooking is another great one that was mentioned, and it goes hand in hand with staying healthy along with exercising.

One I didn't see mentioned was Lego. Fair warning, it can get very expensive, but I found it very relaxing to build something with my hands. Plus, you can just turn off your brain for a bit and it feels great to admire a build after you've completed it.

I started building sets for things I was interested in, like Star Wars, and would watch the movies while building or put on an audiobook.