Personally, I tend to "start" working, then all of a sudden stop to do something else. It's not on purpose or anything, it just happens. I've started "stopping" myself when it happens, and trying to identify why I don't feel like working, and built up a profile of things that I seem to want in order to work. For me, it's:

- Dual monitors - Good music - Actual mouse

For the longest time, I was just never able to work on a laptop, until I realized that the problem was screen real estate and an actual mouse.