If you think you can’t do a thing, you will not be able to do it. If you think you can do something, then you have a chance of achieving it. Believing doesn’t mean you will instantly be able to, but you’ve got to believe that you can, otherwise you definitely won’t be able to do it. I’ve seen a number of people who I thought could do something brilliant and creative but they didn’t seem to believe in themselves and therefore didn’t, or couldn’t, do it.
— Eddie Izzard, Believe Me