Eric Greitens is a former Navy SEAL and the current CEO of The Mission Continues. He is also the author of The Heart and The Fist: The Education of A Humanitarian, The Making of a Navy SEAL, which shares lessons of leadership, ethics and inspiration from his service as a humanitarian and a soldier. Greitens describes how in his experiences mental endurance was more important than physical endurance.

Eric Greitens: One of the things that makes a warrior into a warrior is that they are dedicated to developing their strength in service to others.  One of the things that makes SEALS special is they can be thoughtful and disciplined and proportional in the use of force.  But in order to do all of that, in order to master that, you have to have the self-mastery, you have to have the discipline that allows you to operate in these extraordinarily challenging and difficult environments and still make sure that you are in control of how you’re using force. 

To become a Navy SEAL, you have to pass through the hardest military training in the world. In the course of that training they ask you to do things like swim 50 meters underwater, swim down 50 feet and tie a knot.  There’s something called “drown proofing.”  They tie your feet together and they tie your hands behind your back and then with your feet tied together and your hands tied behind your back, you have to swim 50 meters.  

You pass through another week called “Hell Week,” which is considered to be the pinnacle. During that week, you are pushed to your mental, physical and emotional limits and then beyond.  You're pushed to the core of your character and then you need to look inside yourself to figure out whether you’re going to survive or leave.

My hardest moment came when, for the very first time, we were going to be sent into the tents to sleep.  We’d been up for probably 72 hours and people were literally falling over, and I thought that sleep was going to be blissful.  I laid down and I couldn’t fall asleep.  I could feel my foot pulsing in pain.  

I started to get fearful and I started to panic and I started to think, "What’s going to happen to me if I can’t sleep?  Our class only gets two to five hours of sleep, what’s going to happen to me if I can’t sleep? . . ."

I knew I was going a little bit crazy because a thought actually ran through my mind like, “Well, maybe if I can’t sleep they’ll let me take a nap later,” which of course was not going to happen.  But what happened was, I stood up and I walked outside of the tent and I walked over to this faucet and I turned it on and I put my head underneath and I washed some of the water over my head.  And I turned back to the tent and as I was walking back to the tent I just thought to myself, “This isn’t about me.  This isn’t about my fear and my pain. This test is about my ability to lead and to be of service to the people who are asleep in that tent right now.”  

And as soon as I let go of my own fear and my own pain, as soon as I focused on what I had to do for others, all of that fear and pain left me, and I walked into the tent and I fell right asleep.