<p>It really varies from person to person. Personally, lack of sleep doesn’t really affect me as much as anxiety does. Once I get relaxed, the next thing for me is a constant flow of sugar during breaks (to prevent a sudden sugar crash before exiting the testing center.) Another thing is to stay concentrated and not get bored/distracted. Remember that this is paradoxically a more worthwhile use of 4 hours than hanging out for friends, as it will open doors for you.</p>