I have had some timing issues in the past, so I can relate to how frustrating that can be. But the first thing you need to do is realize that closing down the exam is NOT going to help you. Just finish it out. Who cares if you finish or not. Think about it this way, are you really that much worse for the ware after your last real MCAT? Probably not. You didn't get cattle prodded for not finishing on time or not getting the score you wanted. Noone made fun of you or ridiculed you for not getting what you wanted. All that happened is you got a score that wasn't what you wanted so now you're going to take the exam again, already more prepared than you were last time because you've already sat for the real deal!
With that in mind, relax. You're taking this exam for yourself, noone else. So treat it that way. Don't freak out if you're not where you want to be timing wise, just FINISH the exam and try to devise a plan that will allow you to finish CLOSER to the time you want the next time. Improvement doesn't happen overnight, so don't be too hard on yourself when you aren't having an immediate improvement. Compare your progress weely or biweekly rather than daily. This way you'll be able to see the improvements being made.
Some suggestions for you:
1) Relax, take a deep breath.
2) Think about what you are doing that is causing your timing to be out of sinc with what you want (eg. Spending a minute and a half on basic math)
3) Make a timeline - I do this now with every practice exam and it's effects were immediate. I break the exam into thirds and only check the clock at those times to see if I'm close (if not I speed up, if I'm ahead of schedule I just keep up my pace). For example, in the PS section I'll want to be on Q #20 by 25 mins, 40 by 50 mins, then for the last 12 q's and review of marked questions I have 20 mins left. It's helped out immensely. For Verbal I was always having problems finishing the last passage, so I break verbal up by passages 1-3, 4-6, and 7 with at least 8 mins left.
4) Don't linger on answers. You might not know everything you're asked and if you don't know something or it's not coming to you in the first fifteen to twenty seconds, take a guess, mark it and move on. This feels aweful when you first start doing it, but then you realize you have more time for questions you DO know the answers to and you don't miss any easy ones. This will allow you to have time to go back to the questions you marked and give them a sporting effort.
Finally, relax. You'll be fine. Just finish the exams and keep improving, which you will if you keep finishing.
Also, with the amount of stress it sounds like you're putting on yourself, you should really try to get into some type of exercise routine. If you are already exercising, you should maybe get into some type of Yoga or work out a little harder when you're at the gym (This should be STRESS FREE YOU TIME). This stress you're experiencing is going to carry over into multiple aspects of your life and affect them all adversely if you don't figure out a way to manage it now (but don't stress about managing it🙂, just learn what works for you).
Good luck. If you have any additional questions about time management on the exam feel free to let me know, because I've tried a lot of techniques. 🙂