What's the best non-material investment you have ever made for yourself?

For me, it would be picking up Squash back in JC. It has not only changed my lifestyle, but it expanded my social circle. Along the way I picked up values of sportsmanship, discipline (though debatable), and learnt to socialise through sports. I still try to squash at least twice a week to destress and catch up with my friends. I don't think I can imagine my life without Squash right now. It's so strange to think a sport could change my life so drastically. So I'm just curious, what's yours? :)