Use it or lose it.
My Dad read like crazy, was a jazz aficionado, and a did several crosswords a day. If cancer didn't take him, he'd have been sharp and witty 'till 95.
Me, I mountain bike aggressively once or twice a week, but I need to get back to my daily walks.
Brain-wise I took a job in medical diagnostic devices 13 years ago knowing zero about the subject (the tech or the biology) knowing I'd have several years of intense learning ahead of me, that would essentially never end. I knew it would be really hard, but I also knew it would be good for my brain-health.

