Re-reading Stephen King's On Writing, I came across a sentence that really rang true for me. The first draft, we write to tell ourselves the story. The second draft, we tell others the story.
Right now, I'm 55,000 words into a first draft of a novel. I have no idea how it's going to end! My protagonist has a choice to make. I know what I'd like her to do; I'm just not sure if it's right for her. I tried to plan the whole novel before I started writing, but I didn't feel like I knew her well enough to make the decision. I still don't, but I'm edging closer. I hope by the time I reach that point, she'll do it for me.
Sound schizo? It is, in a way. Characters tend to do things that you never suspected; that you didn't even know they wanted to do. Sometimes when I'm writing, I think: Where did that come from? I love that feeling, as if they're alive and exercising their control.
Ah, the voices inside my head. Am I telling myself the story, or are they telling it to me? (Hums the theme to the Twilight Zone...)