Computer-adaptive tests (where they give you a harder question if you get one right, and an easier question if you get one wrong) mess with your head. They keep you at your maximum level of competence, which fools you into thinking you did much worse than you actually did. Even so, I still don't know how I managed to get a higher score on the analytical section of the GRE than on the verbal. I'm much better at finding antonyms for "apocryphal" than I am at determining whether Bob can sit next to Sally given that there are six seats and Joe can't sit to Steve's right and Sally and Edna have to be across from one another.