Take forgiveness. Two levels here. One level: forgiveness means you shouldn’t develop feelings of revenge. Because revenge harms the other person, therefore it is a form of violence. With violence, there is usually counterviolence. This generates even more violence—the problem never goes away. So that is one level.
Another level: forgiveness means you should try not to develop feelings of anger toward your enemy. Anger doesn’t solve the problem. Anger only brings uncomfortable feelings to yourself. Anger destroys your own peace of mind. Your happy mood never comes, not while anger remains. I think that’s the main reason why we should forgive. With calm mind, more peaceful mind, more healthy body. An agitated mind spoils our health, very harmful for body. This is my feeling.
The Dalai Lama and Victor Chan, The Wisdom of Forgiveness