I think it is hard to let go of the past, when it has made a person what s/he is today. You cannot deny things happened to you, but you can try to live a lifestyle that helps you forget. Even then your past is affecting your present.
Yesterday may be a memory for me, but that memory has grown up and changed - my little children have grown up, and now have children of their own.
At the same time, tomorrow is not guarranteed. I learned this earlier this year when I was diagnosed with cancer. It is hard to be worried about the future when you are deep in dealing with today.
Living one day at a time is all we can do. Nothing can change that.