Never give hope.
0. Have faith in yourself and believe that you can do it.
1. You need to assess your weakness.
2. Work on the weakness.
3. Repeat 1 and 2 above till you have mastered the art.
GMAT can be conquered, but it needs patience and practice. I have read stories of people who got 750 or 740 plus in just a few weeks, but not everyone can do so. At least, I am not one of them. It took me many many months to get past 700. My weakness was English, and I began from basics. See what's holding you back.
You need to search for a wide variety of material. Most of the guys get 100+ more than what they score on Kaplan. Don't burn mid night oil too much a few days before the exam. In case you get too stressed out, you need to tell yourself constantly that GMAT can be retaken and that too without too much of wait.
What was the breakup of your score and let us know in which area you need to work more? This forum is full of helpful guys, and I got a lot of help by reading what others were doing to get a great score. Though I am yet to get where I want to, I will reach there soon.