Plotting the Second Half

Halfway through:
But what's on the dark side?

I've burnt up the first half of my WIP at a rate I'd never imagined possible during NaNoWriMo. But just as I'm about to reach what I've plotted as the low point (the worst that could happen) I feel myself getting nervous about what's to come.

In the plotting workshop I took in September, we talked about how the halfway point of a novel can be the place where your main character hits bottom. Hits it so hard you can hear the thud a hundred miles. Just after that point, your MC realizes she has to change. Something she's doing isn't working. She figures that out. Once she does, she's on an upswing, piling up small victories and realizing new strengths, until the novel's climax (the battle of the book.)

Fine so far, but how do you keep tension in your novel when your character is racking up the smaller victories, and those leading to larger ones, and it looks like all is well?

It's easy to tighten the screws and keep a reader on seat's edge while you're plummeting toward the abyss. I'm not sure it's so simple when the sky is clearing. I'm afraid to be boring in my second half. Like my MC, I'm going to have to change up what I'm doing, and I'm not sure how that's going to work.

In Dan Harmon's plot embryo model, your MC gets what she wants and pays a heavy price for it in the story's second half. What strategies do you have for keeping tension high after you pass your story's midpoint? Do you find you have to juggle the way you think about plot? I have a hunch the answer to this question, at least for me, might lie in the subplot. Tell me your thoughts.