Gau,
You're me 1 year ago. I studied with the
MGMAT books, and the online lecture videos, for abour 3 months. I took the GMAT in Dec '14, and I got a 640. I turned 30 in March '15. I felt this was the last cycle to realistically apply to full-time. I was targeting Top 15, so 640 was not close to enough.
I had previously scored 690-700 on diagnostics, but when I sat for the first test, it was 8am early morning, I was hopped up on caffeine, and I am a night owl. All those worked against me.
After, I rescheduled for Feb 26th '15, and sat down with my
MGMAT books and reviewed all of my CAT exam questions, statistics and areas of weakness. I took more
MGMAT CATs and finally the GMAT CAT and scored a 740 on the diagnostic. For the exam, I scheduled it for a Thursday evening at 4:30 PM; I went to work that day, had my morning coffee, and went to the test after work (no more coffee ahead of time). I was in my element at that point of the day, and I ended up scoring 710.
Lesson is, work harder to understand your weaknesses, take it at your optimal time / conditions, and don't feel discouraged. I got into my goal school (Anderson) and another, and will be heading to LA next fall!