[aterimperator]

This is also mentioned in "Zen and the Art of Motorcycle Maintenance" (which I haven't read in a while, so bear with me). When one of his English students complains she's stuck and can't figure out where to start her essay, he tells her to pick a single city to write about. When she returns later with the same problem, he tells her to pick a single building in that city to write about. When she again returns later, he tells her to pick a single brick in that building to write about. When she again returns later, she comes back with dozens of pages.

I recall there being some comments about how she had to narrow her focus, because when you think of a city you can only think of all the things you've ever been told about that city, or ever heard about that city. Even when you think of a building you can only think of what other people have said about that building. When you focus on a single brick, it becomes clear that no one has ever said anything about it; so you clear your mind and think and write your own thoughts...

Point being, limiting yourself can get rid of certain distractions and make it clearer what your task actually is.