A single powerful metaphor

I don't remember the exact quote, but Toni Morrison talks in one of her interviews about how in the drafting process she's looking out for the one metaphor that will carry her through the book. She says once she has that, she knows what the book is about and the rest just flows.

I thought of that today as I was trying to work on the book--really struggling--and had this image of what it would be like not to struggle. It was a fleeting sensation of having some kind of guidestar that just made it obvious what I was supposed to be doing all the way through the book. I'd be glad to work hard on all the rewriting and revising necessary, if I just knew what to do. My real problem for the last few months is I just plain don't know what I'm doing. This sensation for a second this morning, as I thought I was glimpsing that kind of clear path ahead of me, felt like a major relief, and for a second I felt I just had to have something like that. That it would take away all the burden of this rewrite process.

I don't think I have it though. Maybe I can split the difference and say that I have one for Part 1 and one for Part 2, and even that I'm not sure of.