A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
That happens in marriages, too, and in the other relationships we have. I can't tell you the number of couples I have counseled who, when they are deeply hurt or even just deeply stressed, reach farther and farther into the past to find yet a bigger brick to throw through the window "pain" of their marriage. When something is over and done with, when it has been repented of as fully as it can be repented of, when life has moved on as it should and a lot of other wonderfully good things have happened since then, it is not right to go back and open up some ancient wound which the Son of God Himself died trying to heal. Let people repent. Let people grow. Believe that people can change, and improve. Is that faith? Yes! Is it 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! Well, guess what? That is probably going to result in some ugly morsel being dug up out of your landfill with the reply, "Yeah, I remember it. Do you remember this?" Splat. And everyone comes out of that exchange dirty and muddy and unhappy and hurt, when what our Father in Heaven pleads for is cleanliness and kindness and happiness and healing.
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.
There was only one perfect man who ever walked the earth. The Lord uses imperfect people—you and me—to build strong societies. If some of us occasionally stumble, or if our characters may have been slightly flawed in one way or another, the wonder is the greater that we accomplish so much.