yeah and that your brain fries. this is comign form the fact that some human's brains cant cope with high stress (fear, exitement) and in order to "protect" themselves they "shut down" into sleep state and thus the person falls asleep. now they only do that once the brain is "close to damage" so if you do that too much you may one day actually damage it.
A slipping gear could let your M203 grenade launcher fire when you least expect it. That would make you quite unpopular in what's left of your unit. - the Army's magazine of preventive maintenance.