Learn to crochet. Make afghans or teddy bears for needy children or something. A pile of yarn and a hook will keep you busy (interested, challenged, frustrated) for years. I've been at it for a good 25 years now and I'm still learning new stitches and techniques.
I was just going to suggest the same thing, based on your other thread about "old people" arts dying.
I have plenty of patterns I could send you!
Doing something with your hands in general, whether it's crochet, woodworking, paint-by-numbers (or real painting if you're good at that), building robots, whatever...just the act of creation is very rewarding, especially because you don't have the pressure of a deadline but whenever you do finish you have something to show for all that work.