A very wise priest when I was struggling with this about a year ago pointed me to this. It is taken from the Catechism of Trent. It provided comfort and solace. I pray that it will do the same for you.
This is taken from the area where it was talking about the Lord’s prayer particularaly the petition of “And forgive us our debts as we forgive our debtors.”
But in this matter no ordinary prudence is required on the part of the pastor, lest, knowing the difficulty and necessity of this precept, anyone despair of salvation.
You see I was concerned because I wanted to forgive the people with all my heart, but my heart was still bitter. I was wondering becuase I had unforgiveness in my life did this make it to where I was sinning and I did despair because I thought that I could not partake of the Sacrament of Reconcilliation with the unforgivness in my heart. [NOTE: I wanted to forgive with all my heart and let go of my nonforgiveness of the person involved.]
THOSE UNABLE TO FORGET INJURIES
There are those who, aware that they ought to bury injuries in voluntary oblivion and ought to love those that injure them, desire to do so, and do so as far as they are able, but feel that they cannot efface from their mind all recollections of injuries. For there lurk in the mind some remains of private grudge, in consequence of which such persons are disturbed by misgivings of conscience, fearing that they have not in simplicity and frankness laid aside ther enmities and consequently do not obey the command of God.
Here, therefore, the pastor should explain the contrary desires of the flesh and of the spirit; that the former is prone to revenge, the latter ready to pardon; that hence a continual struggle and conflict goes on between them. Wherefore he should point out that although the appetites of corrupt nature are ever opposing and rebelling against reason, we are not on this account to be uneasy regarding salvation, provided the spirit persevere in the duty and disposition of forgiving injuires and of loving our neighbor.
This gave me so much comfort and still does. In fact there are times where I realize that I am still angry with the people that have wronged me, and I pull this out.
How does one forgive another? Pray for the grace of forgiveness. It is a grace to be able to do so. I wish that I could say that I have attained it, but I have not. I am still struggling to do this. I will pray for you, please pray for me as well.
Focus not on what they are doing to hurt you. Look to Jesus on the Cross instead. Yes I know that this is easy to say, but so very hard to do. It’s not easy for sure, it is a hard, hard, road. But it is a road that is so worth taking.
Someone once said of forgiveness, when one forgives one releases a prisoner, and that prisoner is you. Unforgiveness is a self-affliction, but it can be overcome. Think of Jesus on the Cross.
Just the other day a person who has wronged me much said something to me. I got angry, really angry. I had to go to my room and grab my chotki rope and say on each bead, Father forgive me for being angry, please help me to forgive them as you have forgiven me. Please give me the grace. After a time, I felt better and more at peace.