If you are doing your best, you will not have time to worry about failure.
By the age of twenty, any young man should know whether or not he is to be a specialist and just where his tastes lie. By postponing the question we have set on immaturity a premium which controls most American personality to its deathbed.
Perfectionism is a dangerous state of mind in an imperfect world. The best way is to forget doubts and set about the task at hand... If you are doing your best, you will not have time to worry about failure.