Answer: First, understand that we don't know what really went on in his training. Not saying he was a liar or anything but all we have is rumors.
Second, there was a study on elite athletes, specifically swimmers and cyclists (I heard this on a podcast so not exactly sure....) - the guy was talking about (for lack of the correct term) lactic acid levels in these athletes. For numbers sake, he was saying when the average person's "lactic acid level" (again not exactly sure the correct term, but let's just understand what is being said) is around 25 or so, we'd be on the ground, throwing up and a complete mess. One group of elite athletes were totally fine with a "level 25" and could even function at a high level around 35 or so. The other group of elite athletes never scored about a 10 on the same scale; so they don't even know why anyone would be complaining about being tired.
You can be 100% sure that people at the elite level (and Payton is probably the best football player to ever play the game) are gifted beyond what you can even fathom. If you've ever hung out or trained with or played with a true freak - not the kid that was all-state but the kid who was 370lbs and could run like a gazelle - you realize they are literally a different breed. Add a great attitude, the ability to tear someone's head off and a great work ethic and you have a star.
These guys like Payton or Dan Gable are freaks - not just in their sport but even how they've trained. You can't train like that; you can get motivation from it and draw from it (i.e. we can probably push harder than we think). And I get it - it's motivating to see people who work hard and realize that it takes ZERO TALENT to work hard. I see kids every single day who realize they have 2-3 more gears in their heart. But for 99% of the people in the world; they need to find that balance between smart work and hard work.
And for these 99% - being steadfastly consistent, day in/day out, year in/year out - of good, solid hard work - where you have a good plan and execute that plan with precision and commitment and total belief; you will blow the doors off your reality.