I've noticed that at least some military officers, especially above a certain rank, seem to have this supernatural calm under stress. I read a story about a submarine accident, where some outsiders happened to be on-board, and they said that as the crew starting running around, the captain - who likely had just lost their career - got on the loudspeaker and said, in an almost friendly tone, 'hey, I know your hearts are pump, pump, pumping. Just remember your training and trust each other.' I've seen it in other places.

What is the training or technique used? I'd love to learn more about it.