We talk about forgiveness pretty often. We pray for help to forgive those who wrong us, those who hurt us... But I think, and in my experience, it's been harder for me to forgive myself (at times), then it has ever been to forgive someone else.
So often we hold on to our past mistakes, failures, sins, etc and the guilt that comes along it. We've repented and asked for (and been granted) God's forgiveness - yet WE haven't forgiven ourselves.

"If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness." ~ 1 John 1:9
Does the Blood of Jesus mean anything to you?
Those who constantly struggle with guilt and a sense of shame from their past mistakes, are overlooking or underestimating the power of the Blood of Christ. They somehow have this lurking feeling that they aren't truly forgiven of what they've done; that somehow their sin is greater than the Blood of Christ, although they would never openly say such a thing. One key to freedom is to honestly face the facts: do you really believe that your past failures are greater than the Blood of the Son of God, the creator of heaven and earth? Do your failures outweigh the Blood of Jesus, or does the Blood outweigh your failures?