It will do its best.
It'll put patches on cuts and little muscle strains. It'll up the adrenaline and cortisol levels to keep the blood flowing to your heart and body.
But one day it won't be enough.
It's like a house that's not been maintained properly. Yes there's the odd lick of paint on the woodwork and that slipped slate gets pushed back in a bit of cement slapped on the pointing by the chimney. You keep your hair cut and you dress well and put your make-up on. But that's just the outside appearances.
The inside is what's really important. The next thing you know there's dry rot and the joists are falling in and the walls come tumbling in (sorry if I've used that analogy before, lack of imagination!)
And this is the same with your body. It all mounts up so that one day you go to stand up after shaving, and your back goes. Just like that. You didn't do anything. You can't think of anything you did the day before. There's no reason for it.
Except that there is. There always is. Whether your back muscles have just got weak through lack of use or by being used wrongly. Whether a virus is making its way around while you're immune system was busy just keeping you awake.