My old boss, Kevin Lynch, used to write a television commercial every day, as soon as he sat down at his desk. Not necessarily for one of the agency's clients. And not for an assignment or according to a brief. He did it just to get better at writing television commercials.
The sports analogy goes like this: If you’re a professional basketball player, of course you’ll show up for the games. Of course, you’ll show up for practice. That’s what everyone does. But how often do you go to the gym when you don’t have to? How often do you practice your jump shot when no one’s asking you to? What are you doing to get better?