When something is so emotionally overwhelming that it paralyzes you (emotionally) as though the rest of the world is speeding along and you are frozen. This eventually leads to an emotionally slamming of your mind into the proverbial dashboard of life.
When I saw my beloved husband of 32 years naked in our jacuzzi with that 20 year old, I experienced a horrible emotional inertia. When I regained my senses a week later, I ran over him six times with my Hummer.
The amount of emotional stability associated with an individual as it pertains to how dramatic an event is required to move them to an extreme emotional state.
His girlfriend seems to be able to be moved to tears by such a simple thing as a greeting card commercial. That chick has absolutely no emotional inertia!