why did I do this to myself!

I've wanted to do it since I was in school but I sucked at school since I have no concentration due to medical conditions, so I finally save up and start a online course to help me further my career, I thought I might be able to cope better not being in a class setting, nope my concentration is still bad but it something I'm really interested in so I'm trying my best. the first thing you have to do is write a 3000 word essay! english was my worst subject and I can barely write a paragraph. why do I do these things to myself! it'll be worth it if I pass but I'm so worried I'm gonna fail and can't remember anything I learned in school so Google is my bestie right now. just had to vent at myself for being so stupid.