We remember others for what they have done to us, or how they hurt us. Some of the people we have shared time and space with have brought us good things even, if they are no longer in our lives. You can make your heart hard or difficult to penetrate by closing it, or keeping it from others.
But to build high ledges and walls, where no one can reach you is not living the life you are entitled to live. You are doing a disservice to yourself. You will never get to see the wonder of some things that require vulnerability and openness. You cannot keep the world out and expect to find joy. The past cannot be changed, forgotten, erased or edited. It can only be accepted.