I've never worked towards a specific word count before, but I find that it works for me. It helps to have that goal for each chapter. It makes me stop for each paragraph and wonder: have I really told everything there is to tell? Can the character reflect on this in some way that ties in with a theme?
Sometimes I don't reach my word count goal, and that's just fine. It just means that I've milked the story for all its worth, and to add another word would diminish it.
I love to learn, and being a writer ensures that I'll do just that for the rest of my life.