As to muscle tension/tightness, it's very hard for me to tell because my muscles are always extremely tight due to chronic anxiety. They have been for as long as I remember, the neck and shoulders particularly.

I think that part of what concerns me with my current fic is that I'm pretty much turning the canonical hero into a villain while staying in his first person POV and staying kind of sympathetic to him while he does terrible things. I'm going to have to tag carefully and slap a heck of a lot of warning notes on this one.