To be evolving creatures we need to live in the now and improve our future. Dropping past events and acting in the now and for the future is always the right decision when compared to remorse and regret.
Those negative events you dwell on have already changed your brain chemistry. Trust yourself that this is the case. Even though you may have acted incorrectly or wish that things could have been different so that your life now is different, it is all over now.
I am reminded of the serenity prayer, of which I encourage belief in;
Lord, grant me the strength to accept the things I cannot change,
the courage to change the things I can,
and the wisdom to know the difference
Everyone has their regrets, but the knowledge that remorse and regret are corruptions of hindsight, hopefully can grant some freedom from their mistakes or negative experiences.