@Iluviaporos - A really good advanced first aid course will hopefully simulate some of the situations you might find yourself in. And I think people can extrapolate how they might react in an emergency from how they react in other situations.
Everyone has been in a situation where they've had a sudden jolt of adrenaline. And everyone has been in a situation where they've seen blood and had to deal with it. Even if it's just a friend cutting their finger while chopping vegetables.
You will act in a more extreme way in a more extreme situation, but if you are choosing to work in extreme situations presumably you will be surrounded by people who know what they're doing anyway.