Hi!
Let me begin by saying "Our greatest glory is not in never falling, but in rising every time we fall"
Disclaimer: I am not an expert but just want to help a fellow GMATCLUB community member!
From the little I know:-
1) Since you have scored a 640 in a mock (assuming it was from mba.com, manhattan, kaplan etc) then you have the potential to get a score in the range of plus minus 30 in your real gmat.
2) In the absence of the individual split between Verbal and Quant, it could be helpful to order an ESR (i.e. enhanced score report, if not bought already) from mba.com. You would get enough data points to work on. Then you may pose specific questions in this forum. Maybe we might be able to help you further with specific feedback.
3) Your question is a general question which many have posted in this forum. Maybe you might like to look at them as well.
4) Have a positive mindset about the exam. According to me, getting bogged down and feeling nervous was the biggest contributor in your downfall. Tell yourself every morning and every evening and whenever you feel down, "GMAT is testing some core skills and nothing advanced. Just push yourself with the mantra, "If I can't, then no one can"."!!5) Give at least one mock every week until your exam day. Spend more time in analyzing your results. Improve wherever possible. Develop and improve your timing strategy. There are ways to improve on this front, like (1) more practice under exam conditions or (2) strategically skipping few "above your ability level" questions in few seconds or (3) setting up your sratch pad before the exam to keep a track of time etc or many other strategies.
6) Official questions are like a gold mine. Solve them and learn from them. Analyze even those questions which you have got right. Analyze the wrong options why they were wrong. Maintain an
error log.
7) Develop a clear strategy on how to tackle each and every question type. This will help you in saving time.
8) For relaxing yourself try doing some meditation on daily basis and eat very healthy food till exam. Some physical exercise on daily basis should also be helpful. Dont study too much just 1-2 days before the exam. Take control over your mind and be confident that you can do it!
I think I have shared few pointers which might help you. I hope some other users will chip in with some other pointers which I have not touched upon.
The will to win, the desire to succeed, the urge to reach your full potential... these are the keys that will unlock the door to personal excellence.
Wishing you all the very best!! I hope you get your dream score!!
Regards,
Manish