«Now go back to sleep, Wang-mu. And you, Master Han– your fatigue is showing very clearly. You’re useless to us if you lose your health. As Andrew has told me, over and over– we must do all we can do without destroying our ability to keep doing it.»
«Xenocide» by Orson Scott Card

I’ve me a few people who run «über-tourig», who run too high for too long (think car engine), burn more energy than they can recuperate and end up burned out. Roughly once a year, usually in the spring. And that’s under normal circumstances. Add other «stressors» (life’s «little gifts») and they can sink.

It’s one of the reasons why I like the quote above so much: «we must do all we can do without destroying our ability to keep doing it». Or to put it in a figure:

You have some resources stored away (left side). When you go through life (right side), you either spend more energy than you currently have, which means you have to expend energy from your storage, or you spend less energy than you currently have, meaning you can store some energy in your resources. If you go through time expending to much energy for too long, you can compensate it for a while. But when the stored energy in resources runs low, you start to take damage, and if you don’t change, you crash.

And yeah, a bit like a stress model in a different skin.

But I find it a useful model. One of the problems however is that «change» actually means changing something fundamental. You can’t just take frequent crash breaks. You have to go through life taking care to recuperate frequently and use high expenditure phases only rarely. After all, they have their place, but they cannot be done all the time.