Congratulations! You did better than most of the testakers on one of the most difficult standardized exams in existence. This is despite the fact the testing pool is made up almost completely of people who have completed (or are completing) a four-year degree, and are probably more ambitious and accomplished than most such students.
Keep in mind that most people never even get a four-year degree in the first place.
So even if you didn't hit your practice average, and decide to retake, don't be overly bummed by your performance -- keep it in objective perspective.