I took the test a few years ago and got a score that I was very unhappy with (640). I can tell you with certainty that the LAST thing you want to do is give up now. I'm taking the test again this week and can say that I had much more difficulty studying this time around because I didn't have the base knowledge. I put the work in, and now I'm scoring between 750 and 780 on my practice tests so I'm feeling good going into the test this time.
My mistake the first time around (and it sounds like this might be yours too) was that I went too gung-ho on practice problems without understanding concepts first. I thought that if I just did problems everything would just click. Bottom line is, there aren't enough problems in the world for that if you start off weak as I did.
Here's my advice:
1) Start with concepts. The Manhattan GMAT books
are the best for this. This is so that, when you do practice problems, you have a better understanding of WHY questions are right vs. wrong. This will help you in three ways. First, when you are doing practice problems, you will be able to process your mistakes and successes much more quickly and more effectively. Second, when taking the test, you will be able to do process of elimination (especially on verbal) to get the right answers much more easily. Third, even when you don't have a CLUE how to solve the question, you know the patterns that the GMAT tests and can 'randomly' guess answers much more effectively.
2) Do practice problems: slowly. Find some moderately difficult questions (any of the Kaplan
books are good for verbal) and work through them slowly and surely. You need to understand every answer choice and every question completely before moving on to the next -- don't be bothered if a single question is taking you 10-15 minutes at first. And for this, it's perfectly fine to go over the same questions you've already done because it is more about the wrong answers than the right ones.
3) Do timed tests. Once you're comfortable with practice questions and you're percentage correct on them, do ONLY timed tests of 75 minutes and 37-41 questions. This will get your brain in GMAT mode and fatigue will become less of an issue. Also, this is where you should address your question of "how do I stay strong in quant." I would advise doing 2 sections of verbal for every 1 section of quant. I had the opposite issue -- I was scoring very high on verbal and when I started focusing on quant my verbal went way down, so I started mixing it in. The 2/1 ratio worked well for me.
The important thing is to stay motivated. It IS very possible to get a high score. For a few people it seems like this takes little to no effort, but for the rest of us bozos the test is quite correlated to time spent studying (and quality of that time). The more you do the more comfortable you will be, and if you invest 3 solid months, you'll be up in the 700's with no problem.