Forgiveness is a promise not a feeling. When you forgive other people, you are making a promise not to use their past sin against them.
Forgiveness is a major part of life that almost everyone has trouble doing. Learning to forgive someone that has wronged us is a very long and difficult process that must be done. Without forgiveness we can not let go of the bitterness and resentment we have towards someone, and without letting go of these things, they start to eat back at us spiritually, emotionally, and eventually physically. When we remain angry for extended periods of time it definitely takes a toll on our bodies, for example, with a rise in blood pressure.