No misery here and it is not needed, because you can do anything you set your mind and will to. Success belongs to those who want it bad enough. Do you want it bad enough? If your answer is: "Hell yeah!" then there will be nothing stopping you from achieving your goal. Go at it with everything you've got and save nothing for the return trip home. Pretend you are swimming out into a large lake with Ethan Hawke, the one who swims out furthest wins. Save nothing for the return swim back to shore and that's how you will win. Don't give up! Don't quit!
If you find yourself wallowing in self-pity and misery, you may be burning out. Take a day off. Yes a whole and complete day doing only the things you love doing. Reward yourself like you never have before because you probably haven't for a long time if ever. If that is not enough, take two days off. But, whatever you do, make it as a day for yourself, for what you want to do, for the things that you think are fun and make you happy. After that, the following day, take 30 minutes to go over a subject for the MCAT. Take a 30 minute break, and go at it again. Work your way back up, then take breaks. Take breaks regularly, but moderately. But most of all, don't give up! You've put so much hard work into this to reach the point of misery, but you got that much more hard work left to finish. Quitting is an option, but furthermore, it is a choice. You can choose to lose, or you can choose to win. Choose to win, trust me, it is actually the easier choice.