Now don't get me wrong, I'm a hacker at heart and love to get under the hood, pull things apart, and put them back together. But the more I do this, the more I hear this little voice in my head say, "Wait a minute. Sure it's cool, but what's the point?"
I have started using an approach that satisfies both my need to hack and my desire to be useful: I try to hack not the stuff that I find interesting, but that which my customers do. It took a little while to get used to (who cares about past due orders when I could be playing with HTML5?), but I have been pleasantly surprised. Grokking someone else's stuff may not lead to many happy dances, but it sure is fun watching someone with money to spend do a happy dance of their own.