A good index of mental health, is flexibility and ability to compromise. Forgive and be tolerant of ourselves, everyone and everything. To forgive is the highest, most beautiful form of love. Forgiveness is healing. If others have mistreated you, they have acted out of ignorance.
Maturity is the ability to bear an injustice without wanting to get even.
Hate and revenge on someone, will cause you to be mentally ill. You will never be happy unless you have your mind free of hate. The victim who will not forgive, will often live in psychological bondage to the victimizer, leading to a kind of paralysis. To forgive is to set a prisoner free and the prisoner is you. A proverb says that when you seek revenge on someone you had better dig two graves.