Use it or lose it. This is all fear-motivated, sure. But it gets me out of bed and into the world every morning. And there I look at some of the casualties I've met who are crippled by their fear. And boy, if ever there was a reason to write a new song or make another phone call or try one more blind date, it's observing how someone else's fear paralyzes them.
Fear is why writers start songs they never finish.
Just plain fear. I don't buy into their procrastinations. Write or don't write. Just don't pretend to be an artist. Have the courage to become one.