Reward yourself for good behavior. It works for kids, why not use it to keep yourself motivated? When you have tasks you don't necessarily like, don't let yourself do the "fun" things like email or Facebook until you've accomplished either a set number of tasks (two or three) or worked for a set amount of time. Then, reign in your fun after 15 minutes or so, and repeat the process again. That little break will help refresh you and make it easier to stay on task during the work time.