Recently I began a job as a bicycle courier, which involves me cycling around the city all day, pretty strenuous work. A few months into the job at the end of the day, cycling home, I would get this horrible pain in my back, and neck, a feeling of tightness. However last night, I got this same pain, but somehow the pain didn't feel painful. It was the same pain which I recognised from before, but somehow, I could feel a small element of pleasure in it, as if the pain and pleasure were the same thing. Although I was feeling the same pain that I was used too, for some reason it didn't bother me the way it used to, and when I really focused on it, I fould that some of what I was feeling was in fact a very faint, but deep, physical pleasure.
I find that this job seems to be changing me faster that anything else before.
Biochemical not spiritual.
Endorphins. Google it.