As we review our lives, we become aware of the many mistakes we have made- things we would do differently, if given a second chance. Our regrets can be useful reminders of how to do better the next time a similar situation arises. But it is one thing to learn from past mistakes and another to make ourselves miserable about them.
We must learn to forgive ourselves for past errors that we made because we were unprepared, or unaware of the consequences, or ignorant of better options that might have been chosen.
Regret can be instructive, but remorse is a waste of time.