However, it's important to remember that writers are individuals, and what works for one writer may be disastrous for another. For someone who needs to overcome a habit of endless fiddling and procrastinating, the pressure to make word count may actually help get the words flowing by getting the internal critic to be quiet. For others, the pressure may result in a "deer in the headlights" mental freeze.
Not to mention that it may be different for a given person at different points in a writing career. A beginner may need structure to provide the discipline to apply butt to chair and get writing, while someone who is more experienced may find that structure confining>
However you accomplish it, the most critical thing is to write and keep writing on a regular basis. Stories floating around inside your head don't do any good until they're written down.