I think the body goes into a protection mode when there is pain, and especially if the pain/discomfort is ongoing. It probably becomes a circle of cause & effect.
How often do you see someone with any kind of chronic pain that has good posture, it's pretty rare, usually they are hunched or slouched.


heybro,
Have you tried the yoga corpse pose?
It's sounds similar to the angels thing , only laying down so less gravity affecting blood flow. It also helps the head to be aligned w/ spine more and the shoulders can relax and lower often too.

You can place your arms at positions that are comfortable, then slowly move them up/out as tolerated.

http://www.google.com/search?q=yoga+...w=1360&bih=669