Look Back and Learn
Learning from the past is essential if you wish to reprogram your thinking and change your behaviors from those that cause failure to new ones designed for relationship success. The way you use hindsight is what makes the difference. The practice of using hindsight to learn from the past is useful as long as you don't use it to attack yourself rather than as a way to learn and grow.
Too many people limit the self-examination they do between marriages to this “would have, could have, should have” syndrome. Rather than adjusting the present from the past, they look at prior mistakes and beat themselves up and do damage to their self-esteem. Worse, if you use the past in this way, you may be so busy being self-critical that you don't learn the important lessons lying right before your eyes. If you gently accept past mistakes and then make adjustments in the present, it can be positive.
When you experience a catastrophe you have a choice as to how you will respond to the event. You do not get any choice about the incident. It has already happened. Most people live their lives regretting events that have already happened. Nothing can take you back in time to reverse the facts, and thus living your life as a victim of the past is not wise. So, learn gently from the past, do some individual psychotherapy, but ultimately you need to trust yourself and don't get the “would have, could have, should have” syndrome. The only way to make a new marriage work is to accept the events and mistakes that have already occurred and embrace them as lessons and teachers.