I just Beat The GMAT!

I just took my GMAT after 2 months of preparation and scored much lower than any of my practice tests, and was essentially quite upset by the above score. I used the OGs, Manhattan GMAT guides, and GMATPrep. On 5 Manhattan GMAT CATs and on 4 takes of the GMAT Prep I consistently scored in the 720-740 range, with one score of 770. In fact, my lowest score ever was a 690 (Which was the very first practice test I took). Needless to say, I expected to do better than I did.

My verbal score is pretty reflective of where I had been scoring, but my quant is much lower than where I had been consistently scoring. I am retaking the test, but could use the advice of people on this forum on how best to prepare.

I can't tell if I just had an off day, and am pretty confounded as to what to focus my prep on over the next month. In general, like most people, my weakness is in data sufficiency, so the best plan I can think of is to focus on getting all the data sufficiency questions in the OG right in 2 minutes or less, and really understand why the answer it is what it is.

FYI - I plan to apply to select top 10 schools...HBS, Stanford..

Lastly, I know people say schools like to see scores in the 40s for both sections, but given my quant on this performance is in the 63 percentile, I am assuming this will hurt me for the top schools. Right?

Any advice/thoughts/encouragement would be much appreciated. Thanks in advance!