"When a deep injury is done us, we never recover until we forgive." - Alan Paton 

We will never recover or win anything is we don't forgive what a person has done to us. If someone has hurt us we will not receive anything by hating but to grow bitter and rude. If we the hate person who has hurt us in the past then they person would take pride in what they have done. If we don't forgive then we will never forget that time. And we would always remember what they have done to us. For example if someone killed someone related to you and have hatred toward them then they would be happy and take pride in what they have done. And you don't receive anything good from showing hatred towards them. Or if you do forgive them then it would be a whole different perspective. If you forgive then you would receive something from it. You would be happy that you forgiven them and the other person who hurt you would loose because you wouldn't be mad at them and they wouldn't take pride because they didn't accomplish anything. Or some people would be relieved that you don't hate them.