Mahdi:
Only you can be the judge of your preparedness. Success or failure on the simulator does not guarantee success (or failure ) on the exam. Personally, I was scoring in the 80% range (plus or minus) on full exams before I got sick of doing 4-hours at a pop, then went to quizzes, usually in weaker areas, until it clicked.
In general, however, simulator scores in the low-70s have been correlated with a low pass rate on PMI exam.
Harry