Confession is sort of like taking responsibility. A lot of hurt takes place when we pretend that things didn't happen, or when we pretend that we were completely uninvolved. It's horrible enough when people do bad things. The hurt is magnified when people deny and duck and dodge and excuse. Sometimes we do more damage in the process of weaseling out of things and making excuses, than we did with our original action.
Confession sometimes involves listening to the person who's been offended against.
We may not realize just how much we hurt them. Or they may not realize just how much we've been hurt. It's knowing the wrong, deep down, and owning it. Confession does not always mean throwing a big, emotional scene. Some level of being sorry is probably important.