Mr. Bell maintains that in the middle of the book, we should have a "Mirror Moment." There are two kinds of Mirror Moments- 1) where the lead character is forced to look inside at himself and sort of human being that he is in this point of the story. He sees "reflected" back at him a self that is morally flawed and must decide what he is going to do about it. The 2) kind of Mirror Moment is one where the character does not look at his moral failings, In fact, he remains basically the same person. It's just that in the middle of the plot he realizes he's probably going to die ( either physically,or professionally or psychologically). So the Mirror Moment tells you what kind of transformation your character has.
It's an interesting idea- what do you think?