Nearly 25 years ago, a friend of mine wrote a lovely essay suggesting that people who wish to be happy are shallow and unimaginative. She stated that happiness sapped the creative potential that motivating emotions (like fear, or anger, say) possessed. To truly experience life, she felt, pick another mood. Be angry. Be frightened. Explore base depression, covet prolonged ennui, woo manic fits.
What conventionally-understood-as-negative mood would you seek out, and why?