The stiff Heart questions
The personification of the “Heart” provides a certain amount of disembodiment to the speaker, who perhaps at this point is incapable of responding to the pain and loss they have experienced. Additionally, it allows the narrator to stay anonymous and uncharacterized. This makes sense as Dickinson is contending that this response to pain is universal.
Also, the feeling of “stiff"ness is directly associated with death, especially considering that "rigor mortis” translates to “stiffness of death” in Latin. Obviously, the pain of dying is disturbingly strong and, at the same time, ultimately numbing.
To help improve the meaning of these lyrics, visit “After great pain a formal feeling comes (J341, F372)” by Emily Dickinson and leave a comment on the lyrics box