Why is this so hard?

I am feeling overwhelmed about figuring out how to revise my rough draft of the methods paper. I always used to feel like I was a fairly decent writer but I no longer feel that way. This reminds me of my class I took for ENG 112 at GCC. There was a paper that I had to write about a story that I wasn't that into. I was allowed to redo one paper. The first time around that I did my paper I got a C as my grade. This was after getting solid A's in my last english course so I was surprised to get such a lackluster grade. But not the end of the world. I just redid and resubmitted the paper. Well I also got a C on my second time around and it was very frustrating to me. The professor had very high expectations. My following grades were better but I still didn't see an A. The last writing assignment also included doing some research. I spent DAYS going over this paper. Much of that time was spent sitting paralyzed at my computer trying to figure out where to begin or how to get my point across. The professor looked at my rough draft and said,"Yes!! This is exactly the kind of work I am looking for!". Well it was good to know that there was a way to impress this guy! But the time I needed to perfect that paper was out of the scope of what is usually doable for me. I don't think I am going to be able to make this Methods paper what it needs to be. I actually hate writing classes at this point although I do see their value and the reasons why I need to do them. But math and physics so much more straightforward. I think I prefer that.