Thanks for coming to the session!
Why do you think that you suffer more from mental fatigue on the real thing than on practice tests? Are you doing the essay and IR sections (and taking them just as seriously) on practice tests? Are you limiting yourself to two 8-minute breaks on practice tests?
Are you more likely to hang on and spend too much brain energy on really hard IR or quant questions on the real thing because you know it counts this time?
What kinds of anxiety symptoms do you experience? (We all have at least some anxiety during the test, but some people have stronger symptoms that can affect them more as the test goes on.)
The answer likely lies somewhere in the combination of the above. I'm going to guess that you do let yourself get sucked into some IR and quant questions that, in hindsight, were not worth the mental energy *even if you answered the question correctly.*
You really do have to think of this test as a test of your ability to manage two scarce resources: time and mental energy. There are times when I let a quant question go not because I can't do it (I can), but because the mental energy that that one question would require is too much - I'm not willing to spend it.
In order to manage that well, you have to know that this is what you're trying to do and you have to have the discipline to do it. You also have to know your strengths and weaknesses. I know if they give me something like 3-D geometry (where I'd have to visualize) or a really hard combinatorics, those are going to take more mental energy for me to do - probably too much to be worth it.
What you describe for #1 (SC), by the way, could be one of two things:
(1) This could be another symptom of mental fatigue; your brain is too tired to recognize stuff.
(2) It could also be that you haven't done a good job of studying the kinds of questions that don't contain obvious splits or differences.
This article can help with #2:
http://www.manhattangmat.com/blog/index ... orrection/