Writer without words

I've been "working" on a story for a little over six months, but have yet to commit it to text. Let me explain: I know the protagonist: what she looks like, what she'll do and how she'll do it. She's this other person inside my head. I vaguely know the plot line but it's not set in stone in case I go off on another tangent and explore something I haven't thought of yet. But therein lies the problem. The story may need to be unmovable in order to get my butt into gear to actually put pen to paper or fingers to keys, and get it down.

However, once I get it down I'm petrified that it just won't be as solid a story as I think / hope it is and I'll have to think of something completely different, and my brain doesn't work like that. I hate to leave anything unfinished and that's how I'll feel if I have to leave this story by the way side. You see my completley self-made and utterley ridiculous dilemma or maybe yo don't. Either way I think you'll agree that I really ought to just do it and see what happens which coincidentally is what my protagonist is saying to me, to do.

I think another problem is that I'm getting distracted by other stories, thankfully not written by me. A Midsummer Nights Dream and The Brothers Grimm folk tales are on my desk as I write and the sheer brilliance of them is slightly disheartening to the poor writer without words.