I have often wondered how my body can be so tense all the time but still have no proper body tone/posture. On top of that, shallow breathing and always on the edge of being exhausted. Its like the tenseness and hypervigilance drains me.

This started before adolescence (bad living while growing up), so I am actually not sure if I have ever experienced a well functioning body at all. How it feels. I also think that attempts to improve physically are sabotaged by this chronic, underlying condition, like the response to training is worse when you are physiologically stressed. 

Any knowledge or similar experiences? Am I right in my assumptions and how do you break the evil cycle.