The following comes from an outstanding book I'm reading titled "Damn Few" by Rorke Denver, the former head of Basic and Advanced SEAL Training. The book, which I haven't quite finished yet is a great read into how the SEALS train. If was fascinating to know that not only did they develop roles within the SEALS but in the instructors as well:
The students have a term for the most fearsome instructors, instructors who demand the most, yell the loudest, and seem the most impossible to please. They are the "hammers" -- loud, hard, and unyielding. They are the opposite of the "huggers," instructors who are warmer, friendlier, and kinder. The truth is that BUDS/S (Basic Underwater Demolition/SEAL) need both. The BUD/S huggers, who'd be considered hammers anywhere else, motivate with support, encouragement, and understanding. The hammers motivate by demanding more and more and more.