The Graveyard Book, by Neil Gaiman

“You're alive, Bod. That means you have infinite potential. You can do anything, make anything, dream anything. If you can change the world, the world will change. Potential. Once you're dead, it's gone. Over. You've made what you've made, dreamed your dream, written your name. You may be buried here, you may even walk. But that potential is finished.”