Anatomical details
When I do my shoulder exercises I am supposed to keep my shoulders straight and back (and if I had a dollar for every time I was told to do that growing up I'd be Warren Buffett) which is actually quite hard when the 'natural' symmetry is notably lacking. To counteract this I do the exercises facing a mirror so I can check the set of my shoulders. The down side of this is altogether too much information about the weird floaty bits in my shoulder. One can quite clearly see bits of shoulder boldly going, if not where no shoulder has gone before, at least where one wishes they wouldn't. Anatomy is weird.