I sent a text message out to all of my clients yesterday about this very rule, and I think it is so important that I will stress it again, and no, this is not an April Fools Joke. The 80 20 rule promotes BALANCE. Balance in life is what keeps us sane, keeps us motivated, and is a more realistic approach to attacking a goal or task. This rule says that 80% of the time, or about 1 day a week, you should be giving 100% percent your very best to what you are trying to achieve, and 20% you can be more lax and "enjoy" life (though i find being productive quite enjoyable). In fitness, this would be doing your workouts to the best of your ability, eating to support your goals, and not half-assing what you are trying to achieve. For the general population this rule could be applied to a simple work/life balance. I know a guy who works his ass off everyday at his job, a very important one at that, but frequently goes on vacations (probably about 20% of his life) to balance out the stress he endures. But, doing this allows him to continue to perform at his job at the highest possible standard. Guys, STOP justifying your mistakes. Stop thinking you are doing your very best 80% of the time when really it's only 50%. If you go to work or the gym and don't give it your best effort, and then do whatever the fuck you want on the weekends, you are NOT following the 80 20 rule and you won't see your body change, an increase in income, whatever. Make the sacrifice, do your shit, and then enjoy the spoils once you've EARNED it. On the other hand, don't just try and conquer the world overnight because that is also not a balance and you may very well find yourself burned out after a few days/weeks/years.