>>76637913
Stressful high speed job, so their brain thinks they're in combat mode. Somehow they think they really are in a warzone, so they develop this "warrior" complex because they are not affected by the losses of real warfare.
Basically the adrenaline minus the danger and loss equals the false sense of being a badass warrior.
Nurses and doctors in trauma centers have this too, but their jobs actually matters and they experience the loss and death, so they don't have the "badass" complex, just the depression.