Exams do have a purpose, but they shouldn't be used to assess the recall of meaningless facts.
There are ways to manage exam anxiety so that it doesn’t hugely impact your performance.
An intense night of study won't help you remember information in the long-term – and the stress of revising under pressure will likely impact on your sleep and thus your exam performance.
Mind blanks are typically triggered in response to a perceived threat. The chemical process that takes place essentially clears out your working memory, quiets logical processes, and walls off memory.