"It's like making a movie: All sorts of accidental things will happen after you've set up the cameras. So you get lucky. Something will happen at the edge of the set and perhaps you start to go with that; you get some footage of that. You come into it accidentally. You set the story in motion and as you're watching this thing begin, all these opportunities will show up. So, in order to exploit one thing or another, you may have to do research. You may have to find out more about Chinese immigrants, or you may have to find out about Halley's Comet, or whatever, where you didn't realize that you were going to have Chinese or Halley's Comet in the story. So you do research on that, and it implies more, and the deeper you get into the story, the more it implies, the more suggestions it makes in the plot. Toward the end, the ending becomes inevitable."
~ Kurt Vonnegut (Nov 1985 issue of Writer's Digest)
I think that this one paragraph is some awesome advice. It speaks to me on so many levels.
First, it says to me write. No matter what just write. If you just write and keep writing something might sneak into your story; something you didn't even think was important and that thing might unite your entire story. Sure, you will write a bunch of crap and fluff before you get there. But as long as you keep writing it will show up. You just have to watch out for it. Oooh... Like a four-leaf clover.
Second, it tells me that your second, third, zillionth draft will require as much work and research as your first draft. While that might seem a bit depressing it should be fun. Sure, it'll be more work, but it'll make your story better.
Third, it tells me that that saying "life if what happens when you're making plans" is applied to writing too. You might have the main plot all figured out, but that's not where the real story always it.
So just go with it. Trust yourself. Trust your writing. And trust that you have something important to say. The story speaks to you, it might talk to you in another language sometimes and then you have to translate it, but it's always there.
Keep it up.