After all, I think you are right. I did not REALLY know why the answer is right or wrong. Sometimies my mistakes was due to careless, sometimes I messed up rules. Well, I am not native speaker and I did not practise english grammar a lot during my life so it was almost a new field for me.
I agree with you, GMAT prep result was really similar with the real test results. So GMAT prep is really good predictor, maybe math was more challenging, but not really much.
I try to relax and continue my journey. Thank you for advices.
after reading your post .. What I can suggest is that although you have solved the questions of OG but you are not sure why answer is correct. You may know answer by heart but do not remember what is logic behind it.
GMAT test your logic. hence quality of questions matters not quantity of questions. As it is very rare that you will see a questions which you have solved during your preparations.
Have you gone through Manhatten SC guide .It is quite good. Also when you solved questions in second shot .....did you note down the reasons why this questions are wrong what is rule.... have you seen similar questions in past ...try to recall.
Ex. generally Being is incorrect...or if there is a modifying phrase in starting of question then it should be followed by a noun which is modified.. or if idiom is used.....
Also try to keep a error log
By the way what was your score in GMATPREP. GEnerally it gives a good idea of what may be your expected score.
In this website you also have a good tool. Gmat score estimator. You can put your score and check result. If you did not write eassay and argument during preparation and if you select your efficient poor + your GMAT prep score..It will predict near to your actual result. you can try that also. but in the end it is tool not official score card.
Also have you also practiced essay and arguments while writing full lenth exam which is escapade by most of people. If not then they may also be responsible for your low score.
Also you said you was just fed up with your preparations in two months....if that had been case why did not you planned for a night with friends or a short trip to somewhere just to get relax and refreshed. It is quite hard to keep oneself motivated.
Never the less everything is possible as far as you are optimistic and ready to conquer the world.
Take a rest for few days and think about your future plan what you want to do.
There are so many good GMAT strategy questions posted in this forum. just go through it. they are quite usefull.
In the end best of luck for your future exam.