brevity/sewing pains

I have one more day working as a stitcher.  The hourly wage sometimes feels luxurious (as opposed to the flat fee payment I often get).  The lack of responsibility is refreshing... and yet it grows old quickly.
Sitting in bad chairs doing repetitive work takes its toll on the body.  Daily trips to the gym help and yet my right knee aches from the up and down and side to side motions required to operate the machine.  My back hurts from the lack of support, my left shoulder has developed a large knot that has become persistent and my ass is getting sore sooner and sooner in the day.  I really don't know how people do this all year.  I especially pity the stitchers who have (and do) have to do this work in cramped, dark sweat shops. Ouch.  I am ready to get back to my other jobs.