You have to have an end time to your writing session. If you're going to sit down at a desk with a problem and do nothing else, you got to get a reward for that—and the reward is the alarm goes off and you're done. You get up, and walk away, and go have some cookies and milk, you're done. If you have the guts and the balls to sit down and write, you need a reward at the other end of that session, which is stop now, pencils down.