This is an excellent essay written by Paul Graham.  It's full of the kind of information many people come to discover too late in life.  The kind of information people wish they had understood when they were younger.  Well, if you're still young, here's a chance to get ahead of the game.  Luckily for me, I know everything already, so it wasn't necessary for me to read it, but you can use all the help you can get.

How to do what you love