Most people think of forgetting as a serious drawback. But to me, it has a great advantage.
If you did not forget, it would be utterly impossible to serve G-d. You would remember your entire past, and these memories would drag you down and not allow you to raise yourself to G-d. Whatever you did would be constantly disturbed by your memories of the past.
The past is gone forever and need never be brought to mind. Because you can forget, you are no longer disturbed by the past.
The best advice for this is simply to forget. As soon as an event is over with, forget it completely and never think about it again. Understand this well, for it is a very important concept.
Reb Noson of Breslov; Rebbe Nachman of Breslov. Rebbe Nachman’s Wisdom #26