How to diminish hurt and easy to forget???

There is a big difference between forgiving and forgetting. Even if you do forgive someone, it doesn't mean you should forget, lest the same thing that hurt you happen again. Learn from it, if you can. Emotional pain doesn't go away easily as you've said. It takes time. As time goes by, the pain does diminish some, the more time that goes by, the easier it is to think about it and not be as bothered as you were before. I am not saying that the hurt will disappear, it just won't matter so much anymore. Forgiving someone is a very good thing, it's ok to remember something that someone did to hurt you it does not make you insincere.