There is need to forget all about the past and its headaches and move on. This is particularly so if say the past was not all that pleasant.
Dwelling in the past will only succeed in hurting you. So, if there are people who hurt you so bad or if there are are some painful and bitter moments that you went through like friends or family betraying you, just let it go.Forgive whoever hurt you and if anything, see the past as a learning experience and move on.
Otherwise as long as we live in this world, there are sure people who are going to hurt us in one way or the other.So in essence, the world will always be just that-unfair and cruel.