For as long as I've been plotting out WIP #1 (3+years now), there was one scene that I KNEW I needed, but that I could never write convincingly. The idea was to have my main character and her love interest have a bitter argument, and for the love interest to resign from his job and storm out. And no matter how hard I tried, I couldn't come up with a good motive for the fight. No matter how I thought of it, it felt contrived and forced. A deus ex machina for the sake of plot progression.
And now, as I start working through this rewrite, my main character has evolved beyond the two dimensional person she was. And it occurs to me that perhaps having them fight is not the right way to go anyway. Maybe, I couldn't come up with it, because that's not how the story is supposed to go? I mean really, all I need is to have him leave the building he's in for the plot to progress. Could he not do that just as well after a moment of tenderness between them? I think it would still accomplish the same thing emotionally (for the reader).
I find this an interesting concept to explore, and it would fill in one of the huge gaps that I was struggling with in the original writing.
Yay for rewrites!