GMAT Strategy

Now I stuck at score 550, but don't know how to improve.

here are my things, pls help me.

(1) I redid the prep2 and prep1 several times to get 700+, sometimes I get 700+ sometimes don't.
But the thing is, If I do it repeatedly, there are some new questions I can learn from, but hard questions's answer that I already know and I chose them, no matter what I still get 700+ anyway.But if I don't do this test repeatedly, I don't what material I can use to help me improve to 700+,

(2) Then you would say OG or manhanten materials, however I think when I do OG, (well, most of questions I already did and I know the answer), I am very confident at doing them, and I think I alraedy memories all the key points, there is no need for to redo OG again and again, I think it won't help to get 700+. Manhanten materials as well.

Here I come up strategy,

(1) I redo the prep1 and prep2 several times , and memerozie all the key knowledge points, and review them. Then I do the manhanten free test to get my score.

Does it helpful for me to get 700+ in real test.???

Right now I am fighting this test alone, and I quit my job to do it, and I really can't fail this time, but more I think about it I think more I will lose. I don't know what to do???

Pls help me and give me some advice, good or bad, all ok.


ps: Pls don't doubt I am wrong ,because when I do OG questions and memorize all points and do again and it is very easy to get all the answers right, but when I do the prep test on computer, I can't do all the questions right, that why I choose to do prep test to improve myself.

but I know that, gmat test is like there are several difficult questions you need to 100% get it right, otherwise it is impossible for you to get high score, and it is also psycological test, when you meet a difficult question, there will be another harder question come. So when I do the prep I already know the answer, but when I do the new test, I failed. then I look up the explanation, WOW, if I thought that way at beginning then I would get high scores.

Now I really frightened because I STUCK AT BOTTLE NECK and don't know how to improve myself not to get afraid of difficult questions.