Forgiveness is hard to give because it hurts to extend it to undeserving and hard-hearted ones. To release a wrong-doer instead of exacting a just penalty requires that we reach out in love, rejecting the temptation to hold bitterness and resentment. This is contrary to our natural inclinations, thus the old adage,"To err is human, to forgive divine".
Forgiveness is not forgetting the wrong done; some hurts are so deep that this would be impossible. We can forget the anger and hurt we felt, but the act is branded in our minds. Forgiveness takes place when the victim accepts the loss and/or injury done him and deliberately cancels the debt owed him by the offending person.
Anger must be dealt with openly and honestly, not denied or ignored. Either it must be vented in retaliation or the injured party must accept his own anger, bear the burden of it, and confess it in prayer to release himself and to set the other party free. Revenge always hurts the revenger far more than the one at whom it is leveled.
In other words , our pattern must be the grievous and substitutionary death of Christ. He willingly received all the hurt and evil of the entire human race in His own body on the tree (I Peter 2:21-24) to pay the debt for our guilt.
He now offers what He has wrought as a free gift to undeserving and guilty persons so they can be free (Rom. 6:23; John 10:28-30).
As nothing else will, forgiveness takes us into the mysteries of grace where God forgives unconditionally on the basis of the substitutionary payment by another (Mark 11:25-26).
One of the fruits of the Holy Spirit's work in a life is the quality of meekness. It is a quality which is nurtured and abetted by practicing forgiveness.
This highly prized quality will cause us to be able to accept God's dealings with us as good, without disputing or resisting them. Meekness will also cause us to be able to "bear one another's burden's" cheerfully and for Jesus' sake, enabling us to enter into the mystery of Christ's sufferings.
Because unforgiveness, and the resentment and bitterness it generates is so deadly, it is not optional, but necessary that it be dealt with. Cancer and arthritis spirits definitely root into this fertile ground. To be bitter and unforgiving costs far more than it is worth.