I'm not prone to the freak-out, especially while writing. As I've said before, I'm pretty big on structure and outlining, but that doesn't mean I don't make discoveries and revelations along the way.
And sometimes, when you're about two-thirds through the novel, you hit this sudden epiphany, where you realize, "Oh, there's a thing happening here that needs to be this." It could be a revelation about why someone is doing something, or why you've been using a certain storytelling device, or the next level of a character's plan, and all of a sudden, everything clicks.
Almost every time, that's when the story you're writing hits the top of the roller coaster, and then you drop down and it's off to the races. You know the whole story, all the tweaks you need to put in earlier, each scene for later that you're going to need.
It's a little scary, but it's also really fun, because a lot of the time, it's just a matter of how fast you can get the book out of your fingers.
I say this, as I reach the point in the Lady Henterman's Wardrobe manuscript where I am almost-- almost-- about to go over that peak. Almost.
In the meantime, look who was interviewed over at File770. I give up a few secrets for the future. Just a couple.