Screwed up shoulder, take 2

I screwed up my right shoulder again during my upper body workout last Thursday. I felt great about the workout as it was happening, it was only later that my shoulder became cranky. It has remained cranky ever since – going so far as to protest when doing simple things like picking up my gym bag.

I really need to both ascertain what is aggravating it and then do focused, appropriate, exercises to prevent this from happening again.