Your joys and sorrows. You can never tell them. You cheapen the inside of yourself if you do tell them.
You have to master not only the art of listening to your head, you must also master listening to your heart and listening to your gut.
I'm a big, big blues fan and the last several years I've really invested in the blues a lot, and I think my playing is getting better because of it - not necessarily better on a technical level, but certainly on a level of appropriateness.