It’s a Fast Company article from 2004, but still interesting reading:
“[...] Creativity is positively associated with joy and love and negatively associated with anger, fear, and anxiety. The entries show that people are happiest when they come up with a creative idea, but they’re more likely to have a breakthrough if they were happy the day before. There’s a kind of virtuous cycle. When people are excited about their work, there’s a better chance that they’ll make a cognitive association that incubates overnight and shows up as a creative idea the next day. One day’s happiness often predicts the next day’s creativity.”