You build on failure. You use it as a stepping stone. Close the door on the past. You don't try to forget the mistakes, but you don't dwell on it. You don't let it have any of your energy, or any of your time, or any of your space.
“Opinions alter, manners change, creeds rise and fall, but the moral laws are written on the table of eternity.”
“At one time I thought the Editor of the Lancet would kindly publish a letter from me on the subject, but further reflection led me to doubt whether so insignificant an individual would be noticed without some special introduction.”