As Rock750 mentioned, I found that confidence is one of the most important factors when it comes to doing the GMAT. You need to know and tell yourself you are able to do it. This realization came to me after I completed a manhattan GMAT
test. After looking at the solutions to my wrong answers, I told myself that I CAN
get those questions correct. Prior to that test, I never managed to pass the 34-35 range in the quant section. After the test, every test I have taken was above 40 in quant. This was a key moment in my preparation. From that point on, confidence only becomes stronger.
Sort of similar story here. A few days before my test day (5 or so) after I had covered all the quants and verbal bits and literally hadn't any stuff to do but to practice here and there, I decided to take a MGMAT "for fun", just to spot any areas that I might have missed or need to repeat.
Quant: same experience as you. I might
had 1 or 2 questions that I didn't know about
Verbal: All SC correct, and ending in V37 or so
Also during the whole time I was ever so relaxed.
In quant my thought was: "I know the basics, if I can answer I will, if it's too difficult then I won't!". Simple as that. Ended up with something like Q44 if I remember, and with 6+ minutes to spare! (because I didn't care much anyway for this mock).
Also, this was my highest GMAT score in MGMAT! What can I say, I think confidence that you know your stuff, plus accepting that there are gonna be questions that you are not gonna be able to answer anyway (plus those experimental ones), took me to the victory I guess.