I don't like to make my heroes screw up. They face danger, they face death, I love creating a good bad guy and a difficult, fraught situation, but my heroes tend to make the right decisions. I hope they're not Mary Sue's, but they do tend to stay, well, heroic.
On the current project, I need to have both hero and heroine screw up badly. They need to be fooled, taken in, nigh on seduced, by the Villain, and it needs to last for whole chapters before they finally figure it out.
And I've just realized that the reason the ending hasn't been working for me is that I've been fighting this. I've been trying and trying to have them figure things out way earlier than they should, and, of course that takes all the suspense out of things, and makes the ending actually rather dull.
There's probably some deep psychology behind this, but I don't have the time to figure it out. I just have to write this d*mn thing, and suffer through it with my people. I'm sure it'll end up being fun around the time the villain gets to gloat, but right now it's a slog.
Cover me, guys. I'm goin' back in there.