Are you bothered by something which has haunted you for a long long time? Do you wish things had turned out differently, or feel you could have handled things better? Are you still sore about it?
First and foremost, you got to realise that what's done is done. It's over, and unless someone invents a time machine, there's probably nothing much you can do to change the past. It's confined to history.
If you allow yourself to be constantly dragged down by it, you will find that you are carrying a very heavy burden. With such a large baggage, it is difficult to live life to the fullest.
If you allow yourself to be greatly affected by it, you might find yourself overcome with anger, bitterness and frustration. These negative emotions are going to lower the quality of your life.
Learn to let go. Let the past be a lesson, an experience to make you stronger. If you can, avoid the same mistakes. But don't let it become a burden to you. ~ami