Billionaire Jesse Itzler participated in a 100 miles Marathon in San Diego. He ran part of the distance together with a team of 6.
Alongside with Jesse ran a US Navy Seal who weighted 116 kg. Yes, 116 kgs – not a typical weight of a long-distance runner.
The Navy Seal had no team and rant the whole distance just by himself.

The Navy Seal finished the run despite breaking small bones in his feet and facing kidney problems.
Very much impressed by this determination Jesse did what successful and rich entrepreuners do when they see exceptional talent. He hired the Navy Seal. The idea was that the Navy Seal will coach Jesse to get the same determination and stamina that he has.

First day of the training the Navy Seal asked Jesse how many pull-ups he can do. Jesse did 8 pull-ups and could not do more. OK, said the Navy Seal, take a break and repeat the 8 pull-ups you just did. After a short break Jesse was able to do 6 more. Good, take a short break and to it again. With no strength left Jesse managed to do 3 more.
“Excellent!”, said the Navy Seal. And now we will not leave this gym until you have done 100 pull-ups more!
And Jesse did. It took him a long time, he had to take several breaks. But he did the 100 more pull-ups.

Navy Seal 40% philosophy means that when a human being thinks he simply “cannot do it”, when you feel that absolutely have no energy left in your body whatsoever.
At this point you have barely used the 40% of your real capacity. I like to think of this example when I need to strech to achieve the needed results.