yeah don't take the damn test until you're ready. and don't rationalize like "omg i studied so hard i need to move on with my life"
no. no you don't. don't just study HARD, study efficiently. i am convinced that the MCAT is designed to test one's level of commitment to the field. as well as other things, obviously. but i personally believe that even the new exam isn't gonna tell adcom's too much regarding how good of a doc you're gonna be (how could it? what standardized exam could tell how one would handle someone in tears when they're told their mother only has 2 months left to live? medicine is more than just a science, it's an art -- and if you can't or do not desire to reach and encounter the patient who is in a vulnerable position with fraternal love and compassion, I would humbly ask you to give up your spot as a medical student and go work in a lab so someone else can.)
the old test's ability to predict future success fell sharply after USMLE Step 1 exam. we'll see what the new MCAT predicts. regardless: you must get past it. you must beast it! it's worth it! 🙂
as to how? i recommend Khan Academy, the official guide to the MCAT exam, NextStep Exams, ExamKrackers exams (not their books), TPR's LiveOnline class sucks but their TPR Science Workbook is good, and a hell of a lot of practice. Berkeley Review made me cry sometimes, but those books helped me get a 129 on the bio section. (my first score was a 7! or a ~123/124!), and finally and most importantly...for the love of God, do every single AAMC question released on their website today--all the Q Packs, and all the practice material for the 2015 exam.