The 40% rule is simple: When your mind is telling you that you’re done, that you’re exhausted, that you cannot possibly go any further, you’re only actually 40% done.
The human mind is an amazing thing. It both propels us forward and holds us back. The 40% rule reminds us that no matter how exhausted we might feel, it is always possible to draw on an untapped reserve of energy, motivation, and drive that we all possess.