Been doing some reading lately on the subject of Will Power and Determination.
Some interesting research being done on these topics, and it certainly relates to the endeavor of writing (Or the attainment of any goal).
One of the more recent findings has to do with the power of publicity...and accountability. Researchers have proven in a number of studies that "going public" with a goal is an important motivator. The drive to avoid embarrassment, maybe? Or social support? Or a combination.
Another finding: Religious people tend to take a "higher" view of purpose, and this helps them through the tough times. If you focus only on the here and now, it's easy to get discouraged. If you keep your vision fixed on the eventual goal (the "why" instead of the "how") it tends to guard against discouragement.
A third concept: "Pre-commitment." An effective strategy for maintaining motivation and drive is realize ahead of time what your chief temptations will be. What is most likely to side-track you from your goal? By recognizing these sticking points in advance, you are more likely to avoid their destructive effects.
Put a plan in place to shield yourself from the distraction. And if you can't avoid the distraction altogether, decide ahead of time how you will respond to it when it shows up.