Any clue what poem this is?

Pretty much, it's about someone who knows they have the potential to be great, and yet they find themselves incapable for no reason at all. All I remember about it is that the author used a lot of opposite examples; how he wishes to be a fireman, but often finds himself the arsonist. He has so many clever things to say, but a "fool" takes over his mouth. I'm probably being vague here; any ideas?