I would second the idea of revisiting an interest you had when you were busy being a breadwinner.
I played guitar and sang from the time I was 13, but was too nervous to do it around anyone other than close friends. Then 17 years ago I found myself on stage with some acquaintances about to sing a song I had learned two days before. (Lead singer couldn't make it).
I realized two things: first, the nervousness didn't kill me. Second, I enjoyed it and so did the audience.
I have been performing in small venues on and off ever since.
I think it has been good for my memory as well since I have built up a play list of over 250 songs by various artists. No books to lug around.
What would you challenge yourself with?
Best
Les