"Blessed are those whose transgressions are forgiven, whose sins are covered.  Blessed is the one whose sin the Lord will never count against him."
-- Romans 4 NIV
God's forgiveness of our sins is conditional.  God requires us to forgive others of their wrongdoings against us in order for Him to forgive us of our sins.  It is in the contract.  Forgiveness initiates within our will. We do not have to have a warm fuzzy feeling about the person we must forgive. We have to be willing first to forgive from the heart.  When we forgive that person, we are not only letting them go free, but we are also freeing ourselves from strong negative oppressive feelings of rejection, anger, bitterness, resentment, hatred, and murder. Once you forgive, you then turn your case over to the Lord and let Him take care of the justice side of your case.  We can trust Him to take care of the wrong that was done to us by another person in this lifetime of that person, or the next. He will repay them; for He is the Judge of all the earth.  We can forgive and forget about it because our hearts need to be protected. He, the Holy Spirit will heal our hearts from the sting of that wrong that was done to us by another person. 
*Let us have an ear to hear what the Spirit is saying to the Church*