The 40% rule is a very simple concept. When your mind is telling you that you’re done, that you’ve exhausted all resources, and you just cannot push yourself anymore – you’re actually only at about 40% of your capacity. When you want to quit, you’ve used up only 40% of your mental and physical potential. We are capable of so much more than we think, and if we push past our mental walls, we can do incredible things we never even thought possible. When you put it that way, it does seem a bit silly to quit with 60% still left in the tank, doesn’t it?
