Well dreaming is the core value when you make up fantasy... I mean fantasy comes from our imagination and that is kind of what dreaming is. So I would say that dreaming does not really take away from your writing, it adds to it.
Dreaming is an involuntary act. You can use it, like you can use every other aspect of your existence, for inspiration. But inspiration is only the first step. You still need to take conscious, purposeful action to convert inspiration into a viable story.
It is possible if you meditate etc to control your dreams, they don't have to be entirely involuntary or outwith control.