I suggest you don't give up! As long as you have sufficient time to re-take the exam, you will do fine, and it's only a matter of time. Maybe you are not in it yet, if you really study like CDer, you will be like anyone else who got 700+
Haha, you are not alone. Actually my situation is pretty close to yours. I did GMAT twice in Aug. and Sept. with the score 610/49/25/5, and 620/50/25/5 respectively. Every time I take mock exams such as (hoho) Prep and Manhattan GMAT, I never got the overall score below 650. But, the reality is reality!
Anyway, per to your expectation of overall score, my suggestion is: try to hammer CR and RC as accurate as possible and leave SC along. Otherwise, you might be distressed again. However, SC is crucial if you want 700+. Good luck Gmat buddy, your fate is in your hand, you are not alone in this battle.