Theodore Roosevelt.

its not the critic who counts,
not the man who points how the strong man stumbled or where the doer of deeds could have done them 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 enthusiams, the great devotions.
who spends himself in a worthy cause.
who at best knows in the end the TRIUMPH of high achievement;
and who at the worst, if he fails,
at least fails while daring greatly so that his place will never be with those timid souls who know neither victory nor defeat.