GMAT Strategy

Hi all. I took the GMAT last Saturday. I got a 650 (Q43 V37), which is below my target score by about 50-70 points. I scored above a 700 on both the GMATPrep software exams and on the last 3 MGMAT CAT tests that I took (all within the last few weeks). I'm pretty sure I know what went wrong but wanted to run it by some of you guys to make sure I'm not way off base. I was on question 31 of the quant section (feeling pretty good about the questions I had answered so far) when I realized I had about 2 minutes left. Normally by this point I start guessing, because guessing incorrectly and finishing is better than leaving things blank. I must have spent too much time on that 31st question because the section timed out, leaving me no time to guess on the last 6 questions. I got incredibly upset by that because it was a silly avoidable mistake and I know it incurs a huge penalty. I tried to get refocused but I'm pretty sure it negatively affected my Verbal score because of my mental state. Obviously you all weren't there with me taking it, so you can't know for sure but does this seem like a plausible explanation for what happened and why I got a much lower score? I want to make sure I study effectively before I retake it in a month. Thanks so much.