I'm a musician. I've released two albums and one demo this year, all written and performed entirely by myself.
To offer the counterpoint to all of the more positive and neutral examples given of the creative spark, it's just some other secretion for me. It's about as romantic as pus and coagulating blood. All of the other alternatives of getting this sort of thing out of my system are quite harmful, to myself and others. I write and record so those thoughts and feelings don't have a chance to hurt. However, by containing all of that part of me in this one activity I'm able to function in a healthy and empathetic way.
I guess the shorter answer is something like "to keep my even strain."