The reason its important to push hardest when you want to quit the most is because it helps you callous your mind. Its the same reason why you have to do your best work when you are the least motivated. Thats why I loved PT in BUD/S and why I still love it today. Physical challenges strengthen my mind so Im ready for whatever life throws at me, and it will do the same for you.

Can't Hurt Me by David Goggins