So the Greeks, well Aristotle really, argued that one of the reasons to go to the theater was to experience catharsis, literally, a kind of emotional purging or cleansing. The idea was that you'd go to the theater and get so wrapped up in the characters lives, so involved in the emotions, the actions, the "pitiable and fearful incidents" that you'd get all worked up, just like the characters, and then at the climactic moment you'd have a little emotional orgasm of sorts that would release you of the fear or pity in your life. And you'd leave the theater refreshed and ready for another day...