Rules of Programming: Have Fun!
This one applies to more than us developers, but still.
It's very important you have fun doing the stuff you do best, whether it's at work or somewhere else. If you have fun, it's easier to excel and make a great career of your craft, it's easier going to work and you'll find your whole life much more meaningful. You'll probably also produce more quality work if you have fun while doing it!
And if you don't have fun at work, that probably means it's time to make a change.
Rules #10 of programming:
Have fun!