Time well wasted.
(honest question. I did used to consider fun stuff to be time wasted, but as I've gotten older and am paying the price for a long-term high stress lifestyle, I'm starting to think differently about it)
If you haven't read them yet, "Surely You're Joking, Mr. Feynman", and "What Do You Care What Other People Think" were great reads in my 20s.
And then he goes on to win the Nobel prize because of it..