The bad parts of an experience are what make the best stories. No one wants to hear you say 'I had a nice time. It was great.' And so on. They don't want to hear the same thing over and over again. They want a story no one else can tell them. If all you experience is good things, you won't have a story to tell.
My teacher said this to me once. I agree. Also, this is a kind of explanation for Underrated. It's why I think demons have a story to tell; why they're more interesting.