Forgiving partners when they make benign mistakes like forgetting to pick up the dry cleaning is good. Forgiving serious negative behaviors, such as relationship aggression, can have unfortunate consequences. In a recent study, newlyweds were tracked for four years. Men and women who were more forgiving, in general, experienced continued physical and psychological aggression across the course of their marriage whereas less forgiving partners experienced reduced aggression. Forgiveness may reinforce negative relationship behaviors like violence.
McKnulty, J. K. (2011). The dark side of forgiveness: The tendency to forgive predicts continued psychological and physical aggression in marriage. Personality and Social Psychology Bulletin, 37, 770-783.