Anger, bitterness and Unforgiveness can lead to health problems:

Unforgiveness is classified in medical books as a disease. According to Dr. Steven Standiford, chief of surgery at the Cancer Treatment Centers of America, refusing to forgive makes people sick and keeps them that way.
With that in mind, forgiveness therapy is now being used to help treat diseases, such as cancer.
“It’s important to treat emotional wounds or disorders because they really can hinder someone’s reactions to the treatments, even someone’s willingness to pursue treatment,” Standiford explained.
Of all cancer patients, 61 percent have forgiveness issues, and of those, more than half are severe…
“Harboring these negative emotions, this anger and hatred, creates a state of chronic anxiety,” he said.
“Chronic anxiety very predictably produces excess adrenaline and cortisol, which deplete the production of natural killer cells, which is your body’s foot soldier in the fight against cancer,” he explained.
Feeling bitter interferes with the body’s hormonal and immune systems. Studies have shown that bitter, angry people have higher blood pressure and heart rate and are more likely to die of heart disease and other illnesses.

One of the hardest things is trying to forgive when we carry the offense for others. Abused children, e.g.

Forgiveness is an act of the will
We may not feel like forgiving, but Forgiveness is an act of the will, not of the emotions. It is a decision. We decide to obey Jesus and forgive and our emotions get cleaned up afterwards. We will never feel like forgiving beforehand.

Matthew 18:21-35 Then Peter came up and said to him, “Lord, how often shall my brother sin against me, and I forgive him? As many as seven times?” Jesus said to him, “I do not say to you seven times, but seventy times seven. “Therefore the kingdom of heaven may be compared to a king who wished to settle accounts with his servants. When he began the reckoning, one was brought to him who owed him ten thousand talents; and as he could not pay, his lord ordered him to be sold, with his wife and children and all that he had, and payment to be made. So the servant fell on his knees, imploring him, ‘Lord, have patience with me, and I will pay you everything.’ And out of pity for him the lord of that servant released him and forgave him the debt. But that same servant, as he went out, came upon one of his fellow servants who owed him a hundred denarii; and seizing him by the throat he said, ‘Pay what you owe.’ So his fellow servant fell down and besought him, ‘Have patience with me, and I will pay you.’ He refused and went and put him in prison till he should pay the debt. When his fellow servants saw what had taken place, they were greatly distressed, and they went and reported to their lord all that had taken place. Then his lord summoned him and said to him, ‘You wicked servant! I forgave you all that debt because you besought me; and should not you have had mercy on your fellow servant, as I had mercy on you?’ And in anger his lord delivered him to the jailers, till he should pay all his debt. So also my heavenly Father will do to every one of you, if you do not forgive your brother from your heart.”

The Word Translated as Jailer: Strong’s 991 βασανιστής (basanistēs), οῦ (ou), ὁ (ho): n.masc.; ≡ Str 930; TDNT 1.561—LN 37.126 prison guard, torturer, jailer who tortures (Mt 18:34+)

There is a difference between forgiving people and forgiving their sins (what they have done to you or to someone else).

My Story
Kicked out of church… forgave the people, but bitterness remained..
Forgive the sins against me. Caused release.

John 20:23 he breathed on them and said to them, “Receive the Holy Spirit. 23 If you forgive the sins of any, they are forgiven them; if you withhold forgiveness from any, it is withheld.”

Dealing with Abuse: Excusing vs forgiving.

1. Recognize the offense as a sin against you
2. Anger is necessary and appropriate response to violation. Forgiveness should end in reconciliation, not just avoiding Agape Love is learning to love others with their faults.

Be angry but do not sin; do not let the sun go down on your anger, and do not make room for the devil. Eph 4:26-27

Forgiveness is NOT reconciliation.
Forgiveness does not mean trust is reestablished unless the behavior changes.
Forgiveness does not depend upon their apology or recognition of wrong. Forgiveness is for YOUR sake. Reconciliation requires the other party to recognize their wrong and ask for forgiveness.

Matthew 18:15-18 “If your brother sins against you, go and tell him his fault, between you and him alone. If he listens to you, you have gained your brother. But if he does not listen, take one or two others along with you, that every word may be confirmed by the evidence of two or three witnesses. If he refuses to listen to them, tell it to the church; and if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector. Truly, I say to you, whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven.”

Some Forgiveness requires a daily repetition and does not always end in reconciliation. It takes two to live in peace.

Romans 12:16-21 “Live in harmony with one another; do not be haughty, but associate with the lowly; never be conceited. Repay no one evil for evil, but take thought for what is noble in the sight of all. If possible, so far as it depends upon you, live peaceably with all. Beloved, never avenge yourselves, but leave it to the wrath of God; for it is written, “Vengeance is mine, I will repay, says the Lord.” No, “if your enemy is hungry, feed him; if he is thirsty, give him drink; for by so doing you will heap burning coals upon his head.” Do not be overcome by evil, but overcome evil with good.”

1 John 5:19 “We know that we are of God, and the whole world is in the power of the evil one.”