When I took the Texas bar exam, a woman sitting next to me spent the entire first day crying. Really, it was closer to wailing. I didn't know her, but I felt very sorry for her. On the second day of the bar, she returned, still crying. She stared bullets at my lucky R2-D2 watch, which I put away because I could see that somewhere in her head she was blaming this entire experience on the fact I had an R2-D2 watch. The third day, she returned to cry even more.
If I hadn't been as prepared for the bar exam as I was, something like that could have thrown me. But I had studied to the point that I believed that even if I literally caught fire during the bar exam, I was still prepared enough to make it through.
There are all kinds of horror stories from bar exams — people throwing up on other people, computer systems crashing, people peeing into their pencil bags, windstorms making the roof bang like a coffee-addled Tito Puente, air-conditioning outages, live target practice happening in the room next door, oil spills that make it impossible to get to the test center, open sewage, wild dogs, etc., etc. Perhaps all the student stress built up over the last few weeks attracts the weirdness, like bugs to a lamp.
Consequently, study enough so that even if something terrible happens, you'll be OK. Set multiple alarms so you will wake up on time. Leave SUPER EARLY for the exam. Be mentally prepared for your computer deciding test day would be a good day to die. Tell yourself that no matter what happens, you've got this. Get mentally prepared and strong in case something goes wrong.
And if nothing goes wrong, great! Just set yourself up so you don't need everything to be perfect on test day. (Alex Ruskell)