Are you overly tired? Or stressed? If tired maybe have a nap, if stressed then do something for an hour to relax. It's the day before, what you do now probably won't effect your grade that much so just relax and do what you can
Hey, is it possible for you to take a break? even if for a few hours?
It is perfectly normal to feel burnt out by this stage. Heck, I had a lot of energy and drive for two months of revision for my law exams, and then half way through my exams I just felt exhausted and like I could not do any more revision.
Definitely have some time to yourself, it is not worth scarificing your health and happiness. If you get some rest you will likely be more mentally fit for the exam tomorrow. You have made it this far, one last push!
I can completely empathise with you OP. As a lazy straight A student with abominable attendence up until GCSE, I continued this pattern into AS, found difficulties with the work and then continually mitched. It wasn't until early April when the school had called and I realised how SCREWED I was for my exams (having achieved CU in january), had to do 7 exams in total including an oral. However, came out with AABC which to this day I don't understand.
Long story short, keep the hard work up for tonight and you will reap the benefits in August.