First, what you describe definitely sounds like mental fatigue, so we need to work on that.
Second, for verbal, you say that RC is your weakest area - but in your resources you list books only for SC and CR. What are you using to get better at RC? (I'm talking about books that teach you what to do, not books that have practice questions. Practice questions help you practice, but they don't teach you how to get better.)
You'll need to do two broad things to fix the mental fatigue issues. First, you'll need to practice in a way that helps you to develop more mental stamina. Second, and just as important, you'll need to learn how to minimize the mental energy expended during the test.
Read this:
https://www.manhattanprep.com/gmat/blog ... you-crazy/And then these:
http://tinyurl.com/executivereasoninghttps://www.manhattanprep.com/gmat/blog ... -the-gmat/The exec reasoning / business mindset is so important because it will help you to decide when something is just not worth the effort it would take to do. It's the same idea as an executive deciding that a certain expenditure is not worth the money. Sure it might help a little bit, but it costs more than it's ultimately worth - the ROI is poor. Those are the kinds of decisions you're trying to master to take the GMAT.
Here's how to practice mental stamina when studying:
Let's say that you're going to sit down for a 2-hour study session. In advance, figure out what you're going to do for the entire 2 hours. In fact, plan extra, just in case you finish early. Then GO for 1 hour without stopping. No checking email, no chatting with a friend, etc. Take a 10-15 minute break, then GO again for another hour, no stopping.
Then stop. Don't do the above for 4 hours straight. It's actually a lot more mentally fatiguing to study than to take a test. When studying, you're both recalling existing memories and trying to create new memories to use in future. When taking a test, you're only trying to recall existing memories.
So if you try to study for 4 hours straight, you'll be so mentally fatigued for the last couple of hours that you won't make very good memories... and your study time will be very inefficient.
But on any day that you're going to study for at least 2 hours, try the above. (And if you want to study for more than 2 hours, just take a substantial break after the first session. My rule is that the break has to last at least as long as the study session itself - so if I study for 2 hours, I break for 2 hours before I do more.)
Regarding that annoying "I narrowed to two and picked the wrong one" phenomenon, here's how you can get better:
First, when you're reviewing, review everything. Identify ALL of the questions on which you narrowed to two and guessed, even when you guessed right. (You are getting some right. But you're not noticing them as much, because you got them right! So you feel like you always guess wrong, just because those are the ones you really notice.)
Then, answer these questions:
1) why was the wrong answer so tempting? why did it look like it might be right? (be as explicit as possible; now you know this is not a good reason to pick an answer)
2) why was it actually wrong? what specific words indicate that it is wrong and how did I overlook those clues the first time?
3) why did the right answer seem wrong? what made it so tempting to cross off the right answer? why were those things actually okay; what was my error in thinking that they were wrong? (now you know that this is not a good reason to eliminate an answer)
4) why was it actually right?
In terms of materials, you need something to help you for RC. This article links to some free RC articles on our blog; if you like them, then you may want to consider our RC book (I wrote the articles and the book, so if you like one, you'll probably like the other):
https://www.manhattanprep.com/gmat/blog ... rehension/Here's a similar set of articles for CR, just in case:
http://www.manhattanprep.com/gmat/blog/ ... reasoning/In terms of how to study, I can't give you a comprehensive study plan; you need to work based upon your own weaknesses, so you need to set up your own study plan (or take a class or work with a tutor - where you'll get a study plan). I can, though, give you advice about how to set up your study plan. And you can feel free to check any aspects of your study plan with me.
Take a look here:
https://www.manhattanprep.com/gmat/blog ... our-score/And here:
http://www.beatthegmat.com/mba/2015/07/ ... s-say-whatAnd here:
http://tinyurl.com/2ndlevelofgmatDifferent aspects are covered in each of those articles. Think about how to weave them together to create a plan that fits your needs. (And, as I said, feel free to come back here and check anything with us.)