Check-itus? The answer is NOT to bone up even more and more on the book, because it is not that extra bit of knowledge that screws up the checkride. Quite the opposite, it is virtually NEVER a bit of knowledge that make the ride go badly, and if you treat the ride as something extra-ordinary and requiring a crash course in esoteric memorization, you will feed the monster that wrecks checkrides. That monster is the self-consciousness that the pilot feels.
How does a check ride go bad? While flying, the pilot starts self-examining and critiqueing, and chews up reserve mental powers saying things to himself like "Oh, gosh, did he see that? What is happening here? Gee, the RPM is off now, too! Uh, Oh, did he see that? What is happening"
No student pilot has much reserve capacity, it is natural that the workload of just flying the thing is high. Once you start down the slippery slope of also maintaining a running dialog of critique, you are dead, and surprises start to mount, you get further behind, and the ride goes to hell.
How do you stop the check-itus insanity? Do not let the self critique start, just fly the darn airplane, and do what you usually do. Have faith in yourself, and learn to stop the internal loop of questions and critiques.