I also have an inner monologue (dialogue?! sometimes it seems as if there's a committee meeting in my head

).
I've been able, over time, to distinguish between when my inner voice is being helpful (like for example when I'm trying to make sense of information, like Lola mentioned) and when it's simply stuck on "repeat" and rehashing useless gunk... that's when I use meditation or Eckhart Tolle's suggestions from The Power of Now to quiet it down.