This is such a great topic. I wish I had known a lot of these myself!
One thing is not really an addition to above, but an angle that has been so huge for me. I have been learning to become fascinated with everything that can be learned from when things don't work - from losing.
I knew nothing about winning/losing, you know? I just thought you had to be a genius and never sweat or else - you aren't worth the air you breathe. That's how my family acts, even if they never came out to say that - they never say otherwise either.
Anyway, the effort you put into trying at anything is huge and builds who you are in larger ways than the activity, or any winning or losing at the activity, or any recognition or no-recognition. The perseverance, the application, the discipline, the insights about how the activity connects with life and other topics, teaching you how to learn something, teaching you how to temper yourself, teaching you about socializing or teamwork and all those lessons while doing a group activity. So many things that are such good stuff and have nothing to do with prizes and honors.
This will sound silly but, one of the best ways I ever wasted my time was in all the card playing I did growing up. For some reason I was always with people, including my FOO, that play a lot of cards. My best buddy in teen years and her family. In college and after we played cards too. Card games are actually fantastic life lessons and I come back to the lessons of cards again and again. So understanding a lot about cards gives me a way to understand other things - especially interchanges (energy, bargaining, luck, skill, value, letting go, mastering your feelings, strategy - so much!). I think the same could be said for some of the other great games such as chess or mah jong, but cards are what I happen to know about.