Jeffrey R. Holland gave this classic talk to the students of BYU on January 13, 1990. He talks about the importance of moving forward, forgiving ourselves and others, and having faith in ourselves and the Lord.
"There is something in us, at least in too many of us, that particularly fails to forgive and forget earlier mistakes in life—either mistakes we ourselves have made or the mistakes of others. That is not good. It is not Christian. It stands in terrible opposition to the grandeur and majesty of the Atonement of Christ. To be tied to earlier mistakes—our own or other people’s—is the worst kind of wallowing in the past from which we are called to cease and desist."
"Let people repent. Let people grow. Believe that people can change and improve. Is that faith? Yes! Is that hope? Yes! Is it charity? Yes! Above all, it is charity, the pure love of Christ. If something is buried in the past, leave it buried. Don’t keep going back with your little sand pail and beach shovel to dig it up, wave it around, and then throw it at someone, saying, “Hey! Do you remember this?” Splat!"
"God doesn’t care nearly as much about where you have been as He does about where you are and, with His help, where you are willing to go."
The complete talk can be found here.