I'm not at University, but I can relate to the failure aspect and wanted to give you my 2 cents.
All through life I've failed with the education system. Terrible GCSE's, Dropped out of college, dropped out of 3 apprenticeships before finally completing one. I built up a reputation with my friends and family as the person who never sees anything through to the end. This was for exactly the same reason you mention above. I would constantly convince myself, there's no point in trying, because when I do try, I fail, so I might as well save me the effort and not try.
I'm now on track for achieving several A's in my A-levels next year which I've self-taught myself in my spare time. How did I do this?
It's the realisation of it all. You need to come to terms with and ask yourself, why am I doing x,y,z? What do you want out of life? Why are you at University? I know as of right now you're probably going through a world of panic and doubt and probably overthinking everything. Take a step back and look at your situation from a third perspective. In reality your situation may seem bad, but I can guarantee there are people going through much worse as I'm even typing this. You're not going to like hearing this, but it's not the end of the world! In terms of deducting a reason to why you're in this situation, I'd need to know more about you. Do you enjoy what you're studying? Are you motivated by it? If not then why are you doing it? Why would you go to university to study something you're not all that bothered about when the purpose of going to University is to graduate with the intention of getting a job later in that field. You'd be stuck doing something you don't really care about for the rest of your life.
I'm a firm believer in that you should always do what you think is right, not what is socially accepted by society or others. Just because a degree means big bucks upon graduating, doesn't mean it's the right thing to do. Find what makes you happy, find what motivates you. Then you won't find it hard to complete these essay's/assignments, instead you will find it enjoyable. Overall you'll live a much happier and more successful lifestyle.
Hope my advice helped you a bit with your worries, stop overthinking! Sorry I can't provide much input on what/what not you need to submit to achieve your grade or whatever. Like I say I'm not clued up on University yet, I'm just a mature student with a lot of experience in self-questioning, overthinking and self-doubt.
Once you find your place in life, everything else will just slot itself into place.