A life spent making mistakes is not only more honorable, but more useful than a life spent doing nothing.
—George Bernard Shaw.
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.
The awesome thing about failure is that it is only temporary. Embrace it, learn the lesson and come back blazing.