Nursing school suck sometimes. It is teaching you a life lesson in humility and what to expect in the real world. I'm not putting you down. I don't think being type A is a bad thing, but, if you never have an experience that shows you that you don't always have control of all things and that you won't always excel at everything then you haven't dealt with the real world.
I used to be a super type A, so I know where you're coming from. Not all the qualities of that part of my personality has gone away, but, life taught me a few things. Sometimes I'm not going to be the best, there is someone who will always get things quicker than me or are better, sometimes I'm not going to be able to control my situation, sometimes things just go to crap and you have to be flexible and deal with it, you gotta work with people who don't like you or vice versa and finally expect the unexpected and you'll never be disappointed.
You've had a realistic slap in the face and it's a tough lesson. While you may not like what your instructor may say, hear what they say and take something from it even if you don't always agree. Show up to class even if you have to drag your rump there and do what you have to do. If you're mediocre, you're mediocre, all you have to do is pass, graduating with honors is cool, but really, nobody cares about that like you do, job-sites don't care usually if you were an A or C student, we all will get paid the same. Some things in life aren't going to let you be a type A person, at least you're learning it now. You now have to learn how to deal and cope with this new knowledge. You can allow it to defeat you or you can embrace and learn from it.