Hopefully temporary sense of doom about my novel

For the first half of the composition of each of my novels I have been consumed by a sense of not knowing what I'm doing, and for the second half I have been consumed by the certainty that I know exactly what I am doing and should not be doing it.--Alice McDermott

Well, I hope I come out on the other side of this looking like Alice McDermott. Because two days ago, as I was quite happily editing my novel, it occurred to me: this is a disaster. The whole concept of the thing is broken; I am forcing perfectly decent characters into a totally implausible situation, which has the effect of making the characters themselves implausible. There is no ground. It's like the Wizard of Oz, when the cyclone comes and picks up the house and Dorothy and Toto and a whole bunch of fragments of their former lives--only in my book, they never land again. The whirlwind just keeps going, picking up more and more stuff, and making everyone, including me, dizzy.

The odd thing is, I am sure that during most of the writing process, this is the effect that I wanted. But why the hell did I want that? Does anyone want that? Maybe I have just been reading too many slow and stately novels lately, and too many realistic ones. Maybe this is simply the horror of commitment, of realizing that the framework of the novel is finally locked in and can't fundamentally be changed. Or...it could just be bad.

This is normal, right? This panic?