One of the weapons that the enemy uses against most of us is our past. He knows that you are likely to loose focus, become weak, depressed and distracted when your past is brought up. So he keeps bringing it up; just when you think you have dealt with it and overcome. It comes up again and again; remember he is an accuser of the brethren.
Have you found that he uses people in your life to bring up your past? Well meaning Christians, friends or family who know your intimate past will throw it at you with the intent to hurt you when you have a fall out!