Learned that from the psychologists I've met all my life, and a book I'm currently reading from Daniel Goleman :v
Anyway, it makes sense. Catharsis is based on letting someone express their inner and repressed (mainly negative) emotions so they can "release" it and so they supposedly see and think more clearly.
But sadly that's not the case in most cases. Letting a person do that will only make those feelings become worse, as such volatile things tend to increase as the person thinks more about them... and there's ALWAYS a point where such feelings may become so unstable and great inside that person, it's completely impossible for them to even use their cognitive mind. And even if the person wasted all his or her energy doing whatever thing in their enraged state (in which after it passed, they may probably not remember what the hell they did), the supposed negative emotions will still be there.
That's why Catharsis isn't really a nice way to solve emotional problems, since the person never really understood what's the source or cause of such feelings (he just manifestasted something, but feelings are easy to manifestate, hard to understand and analyze).
So yeah, revenge may be a (very sadistic maybe) way of Catharsis... but it will solve shit. It will only make the people who wants to get revenge feel even more miserable.
