On a wet Sunday evening, deep in a rabbit hole of motivational YouTube videos, I stumbled across a concept that has forever changed my life. It has overhauled the way I face challenges, and think of my limitations ever since. The 40% rule is arguably a key ingredient in the secret sauce that separates the world’s top performers from the rest of us mere mortals. Before I go hell for leather into the rule however, let’s take a step back, and uncover why our silly little brains hold us back in the first place.


Breakneck Speed

Our brains evolved to do whatever is required to keep us alive, because for most of human history we had to fight tooth ‘n’ nail just to make it through the day. In the past, we struggled to meet the most basic of our needs: foraging for food, maintaining a dry, warm shelter, and battling the ever-looming threat of death by famine, malnutrition, disease, and infection. Our ancestors had so many horrors to overcome, like those unlucky suckers born during the time of prehistoric mega-snakes. *shivers*

In the last century however, our quality of life has advanced at breakneck speed. X-ray capabilities were only uncovered in the last century. In the last 50 years, we went from zero commercial aviation to having over 10,000 giant metal birds in the sky at any given time. Treatment for Type 1 diabetes via insulin was first discovered in 1921, and chemotherapy as a cancer treatment after World War 2.

Until very recently, people still died from scurvy, polio, smallpox, and bacterial infections, without the aid of vaccines and antibiotics. The desktop personal computer wasn’t even invented until the 1970’sMore people than ever in history have access to education, quality food and water, and a safe place to sleep at night. (Read more in Harvard College Professor Stephen Pinker’s book, ‘Enlightenment Now’).


Our Primitive Brain

Quality of life has increased so much this last century that our basic needs are now almost always being met. As wonderful and amazing as the human brain is, it couldn’t possibly evolve fast enough to keep up with  this rapid progression. This has left us with more time to worry about our other, more fickle, human desires. Without the burden of survival, we are free now to worry about our higher-level needs. Things like the need to be respected, recognised, self-actualised, and the absolute best version of ourselves. That’s the trade-off for the luxury of living in the time of iPhones, I guess.

We are still very much primed to react to our environment in an immediate, and automatic way. Our brain exaggerates potential threats despite rarely ever being in danger. For millions of years, this allowed us a split second advantage over our predators and hostile world, ensuring our survival. Our primitive brains have simply not had enough time to adequately evolve to our safer, cozy world.


Mental Barriers

Due to the fact that our evolutionary software is lagging behind, our unconscious brains will remain seeking out comfort, doing everything they can to minimise risk, and avoiding anything which could potentially harm us in any way. The natural tendency of the brain to set boundaries based on fear, risk, and prior experiences (in an attempt to keep us alive), is now not helpful at all. In fact, it can be limiting to the point of sabotage.

We see this come into play in the moments where we run half a mile, but tell ourselves we cannot possibly push further and stop. It happens when you are on day four of your diet, and the temptation of pizza and chips is just too much. You give in, binge-eat, and then give up on your entire diet altogether. It’s what causes you to give up on your dream of starting a blog, though you’ve already published two posts. It tells you that fitting in the extra hours after work is killing you, and you should quit. Our silly brains cannot see that giving in for the sake of short-term comfort now is just not good for us in the long run.


The 40% Rule

We can never completely eliminate the resistance thrust upon us by our brains when we try to do something difficult. However, we can learn to live with it and be stronger than it. You can train yourself to recognise, and overcome the mental barriers that hold you back. This is where the 40% rule comes in.

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?


Origins of the 40% Rule

This inspirational principle was outlined by Californian billionaire entrepreneur, Jesse Itzler, in his brilliant book ‘Living with a seal’. The amazing story begins with Jesse and his team mates, taking it in turns to complete various stages of a 24 hour running race. During the torturous event, Jesse encounters super Navy SEAL, David Goggins, who unbelievably has no team mates to fall back on. It’s not that David’s teamies had backed out, or were held up in a medic tent somewhere; David had actually chosen to run the entire 100 mile race, by himself.

Despite the excruciating pain of broken bones in his feet at mile 70, David never quit, and finished the race. Jesse was instantly drawn to this guy, in awe of his absurd mental determination. How did he manage to get through those last 30 miles?

A few weeks later, Jesse travelled to meet David and convinced him to be his mentor. David agreed, with only one condition. Jesse had to do everything he asked, no exceptions. Three days after their meeting, David showed up at Jesse’s family home to live and train with him for a month, holding nothing but a small duffel bag, and a devilish glint in his eye.

Thus began a crazy journey for Jesse, doing things he never thought he could do, using the 40% rule. With David’s guidance, he pushed himself further than he ever thought possible: doing 100 pull-ups his first day in the gym despite previously thinking he would max out at only 8, and running 4 miles every 4 hours for 48 hours.

**Since I first published this article, David Goggins has brought out his own book called ‘Can’t Hurt Me’. An absolute life-changer.**


Brain Training

Just remember; when you tell yourself that you’re done, you’re really not. It’s difficult at first to disregard the flashing warning signals in your brain, and resist the temptation of comfort. However, you can learn to push yourself through any mental block, and achieve 60% more than you ever thought you could.

All it takes are three simple things: initial effort to just push yourself through, practice to perfect the skill, and the conscious awareness to not give in to the corrupt voice in your brain. When you want to give up, remember that we all have faulty wiring. Our brain is prematurely sending us warning signals, based on it’s primitive desire for comfort. It is wrong. Don’t give in to its shameless deception.

Come to expect the mental resistance. When it comes, be mindful and grateful that you are not even half spent yet. The limitations that we put on ourselves are self-imposed, and we can do so much more than we think we can.

The best thing about the 40% rule is that the more you consciously think about it, and practice pushing past that barrier, the easier it gets. And it doesn’t just apply to sports; it works for all aspects of your life like work and relationships too. With a little focused effort, you can overcome those nagging mental barriers that hold you back.

It comes down to this. The human mind can be your greatest asset or biggest downfall. Only you can choose which one it will be for you.

My advice? Don’t give up at 40%.


P.S. Still curious? I’ve added some videos about Jessie Itzler and David Goggins to the watch section of the website. Find them here.