We let the past go by thinking differently in the now. You are not bound to your past. Some of us feel that if we have done something that we deem as wrong that we can not change; that we are beholden to the past but this is untrue. There is only the now and in this very moment you have the power, given you by God, to change who you are; to be a different person. All you need do is to begin thinking differently; to begin imaging differently and in time your life will begin to outplay these new thoughts and images. How long does it take? It takes as long as it takes you to submit to the new and let go of the past. Simple as that.