I also had a terrible time the night before exams. Morning session went well but afternoon session was difficult. Not sure about the results now. Was consistently scoring around 75% in schweser mocks and around 70% in cfai mocks. Fingers crossed 
i think the only thing that matters is how much u know 
I went to sleep at 10 and I was constantly figuring all kinda formula and theory somehow I got my sleep at 12 and woke up at 2 it was just 2-3 hrs of sleep the night before exam… It happend with me same in level 1
By our age you should know, that if you cannot sleep in stress situations, do not try doing it.