Formula for youth: keep your enthusiasm and forget your birthdays. Genius is nothing more than inflamed enthusiasm. If it were as easy to arouse enthusiasm as it is suspicion, just think what could be accomplished! It is not the critic who counts. Not the man who points out how the strong man stumbled or where the doer of deeds could have done better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs and comes short again and again; who knows the great enthusiasms, the great devotions; who spends himself in a worthy cause. Who, at the best, knows in the end the triumph of high achievement, and who at the worst, at least fails while daring greatly, so that his place shall never be with those timid souls who know neither victory nor defeat. 
-- Theodore Roosevelt