The sad truth is that in most cases stress does not kill you. It just makes you stop living.
My whole life I've suffered from overwhelming stress which has lead to generalized anxiety disorder.
I say "life", but really I have no life, I just go about the days doing things while hurting inside. Stress has peeled off any defence I might have against the world. Slowly, layer by layer, since I was born, stress has chipped away at me. There's nothing left now, only raw flesh around a skeleton.
Everything hurts me... a word, a gesture, a glance. Even the air pushed towards me by the flight of a butterfly is too much to bear.
Damn, that's precisely how I feel as well. Decades of stress has hollowed me out completely. Stress, along with chronic depression, has destroyed any capacity for me to enjoy living. I'm just an empty shell wandering through my pitiful existence, as if I were a ghost lost within a neverending fog.
As it stands, I fall apart immediately at the slightest obstacle. Even the most trivial and petty things, if enough happen to add up, will also cause me to go bonkers. I'm merely a tortured piece of meat, pathetically flopping around and who's of no use to anyone, or myself. The fact of the matter is that I died a long time ago. And every single day I awake I suffer a new death. Even worse than that, every single moment. I don't understand the value in someone like me remaining around. It's totally self-defeating, but since I'm a worthless coward who can't just neck himself on a door knob and be done with it, I'm left shuffling around in a constant fugue of misery, broken up by recurring bouts of intense stress. Like you said, the problem with this kind of agony is that it doesn't kill your body, it only kills your mind and spirit. Which, if you ask me, is way, WAY worse.
Since you've mentioned breathing already, what about the posture?
I'm not sure if you're joking or not, but I have no problems with my posture, nor does it have any bearing on how easily and frequently stress prone I am. The only way for me to cope with stress, is to simply avoid the factors which could bring it about in the first place. Unfortunately, this can sometimes be impossible to avoid, so all I can do in such situations is simply grit my teeth and bear it and, hopefully, shave a few years off my dismal life in the process as a tertiary benefit.