Well, I guess that’s not true. Certainly just hard work is fine, even a normal healthy life necessity.
Think of the heart, which works 24 hours a day and that sometimes over more than 100 years. But the heart can only keep this up because it takes a break after each contraction. You could say, yes, but she has to do that otherwise she cannot perform a new contraction. Exactly, it’s as simple as that, if you don’t rest enough after serious physical strain, you can not re-deliver a proper performance.
You can keep up a lifestyle with to little rest quite some time, but your the quality of your performances will become less and less til you reach a point that it simply stops and you are forced to recover. Think of the weekend headaches, think of burnout.
There are quite a number of people that work themselves into trouble and what happens next is that you lack the energy to take good care of yourself. You start taking fastfood and ready meals. You don’t feel like reading a book or do something to build yourself up and before you know it you find yourself lying on the counch eating trash and watcing trash on tv, in the worst case with a bag of chips. (yes I know how it works)
If you keep up such a lifestyle long enough you have a big chance it will help you dying fast, because this lifestyle helps you to devellop severe chronic deseases like diabetes and cancer.
The example of the heart I hope that appeals to you because it’s such a simple and clear picture about the balance of work and rest.