What should I do now to forget all of sad memories in the past what make me feel hurt and angry too much?

You'll talk out your problems or paint, doodle, or draw, don't dwell on your problems. Stop negative thinking, when you are done for the day do things that you enjoy. If you have to write in a journal and look back on how you felt that day try to change things a little at a time. See the things you cannot handle or change and just leave that up to someone else to worry about. Life goes on, don't waste it on problems of the past leave them where they are and do not go back to where you started at that point in life. Live in the present, Move on and if people keep bringing up the old things in life, you say to yourself, that you are a different person. A stronger version of yourself and you have changed or moved on from that point in your life. If they keep bringing old stuff up is because they live in that moment and not you. You have moved on and replace your bad memories with good ones. You'll be fine, just keep moving on in life strong and leave the pain, baggage and problems behind you. Smile because you are better than all the bad that comes into your life for such a short time. You have the rest of your life to make good. Do just that. Okay?

You have excessive mind activity, I just watched a movie called "Peaceful Warrior" last night and you might want to see it too. All the mind trash inside our minds keep us away from just enjoying our present moment. You don't see what's happening infront of you because you're either so caught up in the past or future that you never live for today, this moment.

This may help:

http://www.wikihow.com/Leave-the-Past-Behind