The most unexpected benefit from forgiving another is the freedom, joy and relief it brings your whole being. The reaction of your body, mind and soul to the hurt and pain you are holding onto may not even been something you are consciously aware of, but believe me it is there.
As Fr. Scott Hurd notes in his book, Forgiveness: The Catholic Approach, "recent scientific studies confirm the healing power of forgiveness. They conclude that people who forgive live longer, healthier, and happier lives," furthermore, he reminds us, "we also deny ourselves God's forgiveness," and "the abundant life Jesus invites us to share." (Quoted from Chapter 2: Forgive for You).
As a kid I suffered from awful stomach issues, I had every test in the medical books. No one could determine the cause, years later, and many therapists later - it was obviously I had made myself physically ill trying to hold in feelings and emotions. I was too young to put words to what I was feeling or why, but it was clear my body was taking upon itself to handle everything. The chosen coping mechanism was neither healthy nor helpful. The therapy definitely helped to begin to reveal the source of that pain, but the roots remained for a long time. They would recede for a bit but then a word, event or image would bring them all rushing back. Until...
Pope John Paul II wrote: "The liberating encounter with forgiveness