What Markos is trying to say is that if you want to train hard, you have to eat and sleep hard, too. As I like to put it, lift like an ox, eat like a horse, sleep like a log.
Your development is a tripod, you know like you use for a camera. It has three legs, Exercise, Diet and Rest.
Each leg has to be kept the same length or else the tripod is unstable and maybe falls over. If your exercise is crap then your diet and sleep can be crap and it won't be a problem. If your exercise is good, your diet and sleep have to be good.
For example, Kyle goes to the gym and does 3 sets each of dumbell curls, alternating dumbell curls, concentration curls, and preacher curls, and after that he does 100 situps. Because that is a bullsht weak workout, he can go and eat Macca's, stay up till 2am drinking, sleep till 7am and get to work, and do it all again tomorrow, no worries. The exercise did not take much out of him, so he didn't have to put in much fuel or spend much time recovering.
But then Kyle gets a trainer who shakes his head sadly at his training and puts him through a proper workout. Kyle squats, deadlifts, and does an overhead press.
For the squats he only uses half his bodyweight on the bar but he does 20 reps, deep, rest just a minute or so then does another 20.
For the deadlifts he uses his bodyweight on the bar, but the trainer makes sure he's careful to use perfect form - which is hard to maintain, because Kyle plays too many computer games and sits on his bum too much, so his glutes are weak and flaccid, so those deadlifts are hard to do with good form, that's why he wants to round his back, that brings his quads in - sticking his bum out is really tiring. So a few sets of 5 reps of those deadlifts really makes him sweat.
After that the overhead press only uses half his bodyweight, but he struggles to get it up for 4-8 reps without wobbling all over the place.
After all that, frankly Kyle is totally shagged. Is he going to be able to do the same again tomorrow? Well... if he has just Macca's for dinner, drinks himself into a stupor and has just five hours' sleep, what do you think?
Of course bloody not.
But if he eats plenty of fresh fruit and vegies, nuts and beans, has some meat, fish or dairy, and fuels himself with starchy stuff, and then after all that has 8-10 hours' sleep... well, maybe he can do it again tomorrow - he can certainly do it after 48 hours.
The harder you train, the better your food and rest have to be.
lift like an ox
eat like a horse
sleep like a log