Besides really bad ailments which restrict you to a bed or location or when your brain gives out (the worst option, but yes, it of course happens; stroke, dementia, etc), I try to build on two things; a) hiking/nature b) brainy hobbies and I try to combine them. I read/write parts while hiking, I program parts while hiking, I interact with my friends while in the middle of rainforests etc. If the a) falls away because of an ailment, I am perfectly happy doing b). I consciously try to prepare for the future as I have seen too many unhappy people and that really is so not needed.