Agree completely. One of my favorite writing moments was after having done oodles of prep work, I sat down to write a scene. I KNEW how it was going to play.

And then, I sat there in the still-dark morning hours, sweat beading on my forehead as I realized that my protagonist's love interest wasn't going to have a quiet dinner with him and talk about what he'd learned on the trip he'd just taken. Nope, she was going to remind him of a promise he'd made -- a promise he had no intention of keeping -- and when she recognized he wasn't going to keep it, she was going to end the relationship.

I agonized over it. My outline called for several more scenes between the two of them over the remaining chapters. They'd have to be junked. Previous scenes between the two of them would have to be rewritten to reflect what I'd learned about her character.

So, after thinking it over for a couple days, I junked the outline, rewrote the previous scenes (and MAN did they crackle with energy), and figured out new ways to finish the story (and get them back together by the end).

Upon reflection, I don't think I had a real choice there. For the character to be true -- to be real -- I had to write what THAT character would do in THAT situation.

this has been posted a while ago, but nothing has changed. universal laws, I guess. exciting!