How do you stay confident when every assignment feels harder than the last?

I used to enjoy writing assignments but lately I have been struggling with almost every one I get. This week my professor returned a paper with so many comments that I honestly felt embarrassed reading them. I spent the next few days trying to improve it but somehow ended up even more confused. Last night I was staring at a blank page and thinking that maybe I need assignment writing help because I seem to be making the same mistakes over and over again. I want to improve my grades but right now I just feel frustrated. Has anyone else gone through this?