Adrenaline, albuterol, the chemistry of pain.
Children overwhelmed and undercomforted will flee. It’s the simplest response to negative stimulus; Occam would approve. So would Morihei Ueshiba. Adults confabulate their reasons, set their destinations at the starting point: it becomes exercise, or competition. Why run without a goal?
Nausea induces flight. Flight induces nausea. Sartre used the sensation to express his horror at existence, but he had to tack on a story (confabulation, you see).
What do you do when the story fails, when regret creeps unchecked up your tightening throat?
Run, run. Turn your head off. The body remembers the way.