Something my dad said about forgiveness in his epilogue on camp tied up with what I read recently in Psalm 51:
Restore to me the joy of Your salvation,
And uphold me by Your generous Spirit.
Then I will teach transgressors Your ways,
And sinners shall be converted to You.
The context is that David has committed adultery and murder, and is now repenting of these terrible sins. Not only does David asks for bare forgiveness, if I may put it that way, but also for his joy to be restored, and to be made useful again. You might have thought that such a fall, which disgraced God's name so publically, would have disqualified him from the joy he used to know or the honour of being a witness for God, but the reality is far from it. God's forgiveness is so complete that He gives us the privilege of usefulness even in areas where we have failed him. He entrusts us with the very things we have proven ourselves unworthy of! David understood something of the wonder of God's forgiveness, and dares to pray like this. In fact, when we fall we must pray like this, or else run the risk of implying God is narrow in His mercy.
Who is a pardoning God like Thee
Or who has grace so rich and free?