DON'T GET STUCK IN THE PAST! Paul warned us to forget those things in our past. He was referring to such things as past hurtful relationships, loss of jobs, the friend that walked away from you, and failures, those things are baggage that will only weigh you down and hold you, hostage, to everything that is behind you.
Remember the story of Lot's wife, God had said to escape from the city and not to look back, and she did. In doing so, she died turning into a pillow of salt.