1) The company it is spent with,
2) The activities it's spent on,
3) The type of responses and stressors such time places on our bodies.
Please don't mistake this to mean that any degree of stress is to be avoided. What I mean, rather, is that since stress, in practice (for most of us) cannot be completely avoided, I find it best to put our bodies under stress for the things that matter to us. Even the subject of our stress affects the quality of our minds and our minutes.
When we suffer by choice for things we believe in and that relationship is in tact, the way we suffer that stress is completely different and dare I say much less "stressful". This relationship becomes especially important when committing to a task regularly is required of us, for long periods of time. Think about an athlete training day in and day out, or a performer required to deliver the same line with the same emotion every show for months. Unless one is tied to a personal cause and passion powerful enough, it is incomprehensible to connect to that type of request of the mind and body. This is why many people who exercise regularly feel lethargic if they miss their work out. The quality of those minutes are super charged with replenishing nutrients in multiple areas so it counter balances the loss of energy and regenerates a surge of it.
Energy Expenditure Energy Generation
Caloric Pre - Setting/Having a goal
Muscle fatigue Post - Accomplishing said goal.
Anarobic Endorphin creating high
Circulation - blood flow to brain
Think more Fluid