A person who doubts himself is like a man who would enlist in the ranks of his enemies and bear arms agains himself. He makes his failure certain by himself being the first person to be convinced of it.
You must understand the whole of life, not just one little part of it. That is why you must read, that is why you must look at the skies, that is why you must sing and dance, and write poems and suffer and understand, for all that is life.