If you have written 2000 words before, than try 3,000 or 4,000 words. The point is to push you out of your comfort zone, and make yourself produce a great deal. If you do not think you can, ask yourself this: If you were told you would be given a million dollars if you completed the task, or that doing so would mean that a loved one would avoid some harm, would you be able to do it?
Of course you could and would; it is just a matter of doing so without accepting the not doing so as an option. Simple, but not by any means easy.