This is a great thread and my first time to see it!
From the perspective of learning about myself, for me it would have to be SERE, with the main learning points being:
1) You are not as tough as you think
2) The occupants of Room 7 were true heroes
3) Pain hurts
4) 110% is not always the right answer
5) The Code of Conduct is real
I also learned that you can get road rash on your face from a vertical concrete wall if you fall asleep standing up!