These are the two fatal mistakes we all make in our lives. We can not change the past or changing adults is even more difficult. These will lead to severe frustration and pain because it is a futile desire. The approach is to identify the problem and accepted. In the case of the parents it could get more complicated. It may require therapy in order to learn how to deal with the situation. You engage in a relationship in order to resolved a conflict from your childhood. Parents who are alcoholic or with mental illness are damaging to the psyche and may lead to self-destructive behavior.
Changing your parents or the past