if i were an American i'd definitely flunk out senior year from things like 40 page writing assignments. How do you even do that?
I assume you mean senior year of college, because I don't think anyone is writing 40 page senior year papers in high school. But personally, a forty page thesis isn't that much. First, its broken down into micro papers that are written over the course of 9 months. You write like 3-5 pages a week and then have your advisor give you the red pen treatment. And then you re-write it and repeat the process until your advisor is satisfied with what you have and then you go forth with the next part of the process. For the first semester it was basically Introduction--Literature Review--Methods--Participants--Procedure... For the second, it was Results (i.e. Findings) Discussion of Findings and Conclusion, which included basically parting thoughts and directions for future research. That really wasn't the hard part for me, as some of the graphs I had to include wouldn't even fit the page in landscape view; thus, I had to add them as a picture even though my advisor didn't like that.
Don't get me wrong, it was so stressful. My advisor (the only advisor who did Senior Research at my University for Sociology) wasn't particularly nice. He'd explain what you did that was wrong and to fix it. If he caught you making the same mistake over and over he would be very rude and caustic. I have heard stories of grown men crying over him treating them like idiots. It was something that I dreaded and was glad it didnt come to that point for me. However, I did have to meet with him every monday to discuss my progress on that paper for 9 months (except for Xmas break) and every week I dreaded it.
To get back to your point: even now when I write I do have a feel like, "Oh this sucks. I'm definitely going to fail this assignment." Even when I write something for myself that is within the context that no one else is going to ever see, I get the feeling that it sucks. One thing I have to tell myself when writing is that what I'm writing isn't necessarily going to be the final draft. It is all I can do just to keep myself from stopping what I am writing because I have a negative view of it.
So, you're not the only one who has those thoughts and feelings. Hell, even on AKP or KPS I have started to type something and edited and re-edited it until I was certain that it sounded right and wouldn't unintentionally offend someone.