I just finished reading a book by Frederick Buechner: Speak What We Feel, Not What We Ought To Say . It talked about the life and works of Hopkins, Twain, Chesterton, and Shakespeare, and how the sadness and tragedy in their lives enabled them to write some of their most sincere work. I was thinking about how tragedy and sadness drive persons to contemplation. In fact, some of my deepest insights took place during a period of melancholy. Why is it that sadness stimulates the mind? Why do we consider tragedy more important than comedy? In any case, I wouldn't be surprised if the reason sadness feels "bad" is related to the fact that people who are sad aren't particularly productive. Perhaps it's another trick of evolution.