To keep pride from rearing it's ugly head, it seems best to forget the "good" I've done. It's easy to forget things anyway isn't it? If it truly is good that we've done, He knows it and He is the One who enabled it, after all. We really aren't building up "good deed capital," we are to be imitating Christ. If we start remembering or thinking on our good deeds, we will start thinking that we deserve special treatment.
If this forgetting of good deeds is a habit, we would be showing an understanding of that delightful future activity of casting crowns at His feet.Forgetting what is behind is not only forgetting the failure and sin that we have fallen into, but forgetting the good things that might also puff us up.