yeah i think i understand what you guys are talking about...
i think guilt can have two impacts to a person. one is internalized where it you don't do anything about it, it sort of consumes you and your focus is solely on the single wrong act and punishing yourself over it. and the other is externalized, it forces you to change your life and how you can prevent that act from repeating itself.
i don't think guilt in itself is unhealthy for a person, but how they cope with guilt can be.