Ernest Hemingway said he loved it when he was done writing for the day, that he could really enjoy his free time then. In other words, if he'd been creative, he was happier.
How about this quote by Gay Hendricks (from his book Conscious Living):
If you are expressing your creative potential, you get to feel good about yourself. If you are not, you don't.
Granted, the quote sounds pretty conclusive, but I think it's true. I'm not going to pretend to understand the dynamic behind it, but I know from my own life that really is the case.
And I've gotten to the point where if I'm not creative during a particular day, that I do feel worse. (And I've also gotten to the point that I crave being creative.)
I think after you get used to being creative for a while, being creative becomes a way of life. And it's a very pleasurable way to live.
So create something—you'll feel better! It doesn't have to be anything big. Just be creative in whatever you're doing. Give it your own personal flair!