Usually we retell traditional stories in order to join ourselves to the past and feel a part of the great events that shaped our people. That is certainly the purpose of the Passover seder and the hagaddah. Deuteronomy indicates that there are also times when we should consider the past in order to reject the things that were done. The point being made is that this is a warning to the new generation not to follow the footsteps of the old. As has been said, Those who do not remember the past are doomed to relive it.
Human beings have a tendency to emphasize our accomplishments and gloss over our failures.
This is true of individuals and of nations. We prefer to rewrite our history in such a way as to minimize if not totally eliminate our failures. We prefer to think that whatever happened was not our fault. The Torah teaches us that on the contrary, it is important to remember what we did wrong, not in order to moan over it but in order to avoid repeating it. Instead of sweeping our errors under the carpet, we should acknowledge them openly and come to terms with them.