"Father, forgive them, for they do not know what they are doing." - Luke 23:34, NIV
If Jesus forgave those who nailed Him to the Cross, and if God forgives you and me, how can you withhold your forgiveness from someone else? How can you withhold your forgiveness from yourself? If God says, “I forgive you,” who are you to say, “Thank You, God, but I can’t forgive myself”? Are your standards higher than His? Are you more righteous than He is? If God says, “I forgive you,” then the only appropriate response is to say, “God, thank You. I don’t deserve it, but I accept it. And to express my gratitude, I, in turn, forgive that person who has sinned against me.”
We forgive others, not because they deserve it, but because He deserves it! The only reason we have to forgive is that He commands us to, and our obedience gives us opportunity to say to Him, “Thank You for forgiving me. I love You.” Our forgiveness of others then becomes an act of worship that we would not enter into except for Who He is and for the overwhelming debt of love we owe Him.
From Just Give Me Jesus