I grew up in a family with mental illness so such stories are always of interest to me. (By the way, I'm not sure I always want to call these malidies illnesses but I have to talk in terms that people are using.) It is a refreshing thought to say that the so called negative emotions can actually be quite benificial.
NPR : The Benefits of Restlessness and Jagged Edges: "I believe that curiosity, wonder and passion are defining qualities of imaginative minds and great teachers; that restlessness and discontent are vital things; and that intense experience and suffering instruct us in ways that less intense emotions can never do." .... Follow the link to read the rest of the story.