The Nac I blues

I'm sitting here studying for test 3 and getting very discouraged . I passed my 1st test but failed test 2. My average now is a 74. I know that i was not very prepared for test 2. But I have studied a lot for this test coming up and I have been doing these nclex questions and getting half of them wrong. I just don't know what I'm doing wrong . These nclex questions have me on the edge . Is there anyone out there who have been in these shoes that can give me some kind of advise on how to understand these nclex questions. It is a MUST that I pass. Failure is NOT an option! Somebody, anybody, please tell me what am I doing wrong.