Nothing in this world can take the place of persistence. Talent will not: nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not: the world is full of educated derelicts. Persistence and determination alone are omnipotent.
Sometimes by losing a battle you find a new way to win the war.
You must accept that you might fail; then, if you do your best and still don't win, at least you can be satisfied that you've tried. If you don't accept failure as a possibility, you don't set high goals, you don't branch out, you don't try - you don't take the risk.
I can accept failure, everyone fails at something. But I can't accept not trying.
Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure... than to rank with those poor spirits who neither enjoy nor suffer much, because they live in a gray twilight that knows not victory nor defeat.