I remember hearing the story that Fields Medalist Klaus Roth was convinced that he could not pass a qualifying exam when he was a graduate student. He was then given a so called practice exam for him to see how he would do. Of course Klaus Roth performed excellently on the so called practice exam. Klaus Roth was then informed that it was actually the real exam and that he had passed. Can anyone confirm this? I didn't see it on his wikipedia: https://en.wikipedia.org/wiki/Klaus_Roth and I didn't see it here: http://www-history.mcs.st-andrews.ac.uk/Biographies/Roth_Klaus.html
I think this article mentions his test anxiety (albeit not the part about the practice exam): http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/naturalsciences/mathematics/newssummary/news_1-12-2015-14-58-30
Roth studied at St Paul's School, and proceeded to read mathematics at the University of Cambridge, where he was a student at Peterhouse and also played first board for the university chess team. However, he had many unhappy and painful memories of his two years there as an undergraduate. Uncontrollable nerves was to seriously hamper his examination results, and he graduated with third class honours.