Hi guys,
The issues you're struggling with --getting down to 2 and choosing the wrong choice, timing, stamina--are not uncommon at all. While I can't give you a magic pill in this post that will make those problems go away, I can suggest some general strategies that might help.
I encourage all my students to think of the process of preparing for the test as training rather than studying. If you were an athlete getting ready for an Olympic event, your trainer would probably have a targeted plan that alternated between concentrated detail work on form (for the GMAT, this means getting your foundation skills up to speed and working carefully and methodically through some problems, without the clock) in addition to the actual "rehearsal" of the full event (CAT exams). There would probably be some middle ground practice too-- maybe not as long as the full event, so you could concentrate on form to some degree, but with enough length and time pressure to stretch those muscles (for my class this means timed sets in
the Official Guide and our online question banks for identified problem areas). And always assess assess assess! You should spend at least, if not more, time evaluating why you got something wrong (or right, but not as quickly as you'd like) than you spent actually doing the problem. It can be very tempting to burn through materials because it feels like "doing," but the greatest jumps in score improvements I've seen have come from those who were not only hardworking, but highly self-aware and willing to take the time to go through the tedium of evaluating their mistakes to make sure those mistakes are not repeated in the future. Getting problems wrong during your study is a *good* thing! It means you have caught a hole in your comprehension that you can work to fill before the test day that actually counts.
In terms of stamina/time management during the CAT itself--again, think of it as a training. You *must* take the full tests to build up stamina. Kudos to Sacnoor for taking the AWA section and identifying that you are worn out because of it--that's good self-awareness and you can act on it to improve your stamina! Don't feel bad if you don't have the stamina now --that's what your training period is for-- and the more you practice in that sweet spot in which you are challenged without burning out the more the test will yield. (VERY IMPORTANT: only you know when you are pushing too hard--burnout is very real and very dangerous so keep an eye out for it.)
For Mahesh: I would recommend devoting serious time to examining those problems that you missed (and the ones that you got right but aren't sure why). Every one is an opportunity to learn more about the rules of the GMAT game--make sure you can identify why the correct answer was correct, and why the others are incorrect. If you don't understand why, post the question here on the forums for some help. If you can't articulate to someone else why the answer is the answer, you haven't fully mastered the question.
For Sebnoor: First off, you seem to already have some great self-observations. Push this farther!
Are you using the splitting/resplitting technique in the SC guide? The technique is just as important as the grammar content, and you can really bank time in the SC area by using splits. It's quite possible to answer some SC questions in 20 seconds--a huge help later on when you need that time for reading passages and CR arguments.
You're right that reading is one of the hardest areas to improve in, but it can be done. The trickiest part is finding the right balance between comprehension and speed. (That's an obvious observation, I know.) After you've completed a CR or RC problem/section, review your diagramming/notations to see if you did too much or too little and adjust to that information the next time around. And for those who are less comfortable with reading, it is that much more important to stay active. If you feel at any point as if the words are washing over you, *stop* and reach into your bag of techniques to get your attention back on track. Are there structural elements you can hang your hat on? Is this particular part of the RC passage rife with details that are not critical to understanding the gist of the passage itself? Etc... And finally, remember that it's about the question! Be just as specific and ruthless in your hunt for what is wrong about answer choices as you are in the SC section.
This has turned into a crazy long post so I'll stop here. Hope this helps. This test is a very well written game with a very specific set of rules--the great thing about it is that the more you play and learn those rules, the easier (and possibly even more enjoyable) the game becomes. Good luck!