"Ninety percent of life is just showing up" - Woody Allen
Imposing rules, quotas, and expectations on myself is counterproductive. It may not be so for everybody, but it's certainly the way I work.
The best I can do is to ask myself to show up every day and take one step in the direction I want to go. How big of a step that one step is varies from day to day, but what really matters is just showing up every day.
When I set crazy expectations for myself (e.g. 'write 25 percent of this book in one sitting'), I am less likely to show up. When I show up and take that first step, work gets done. That's better than nothing.
I have the complete power to strip away those rules and expectations I impose on myself. When I do, it's immediately easier to get back to business. That makes me feel unstoppable.
Now, if only these books would write themselves!