In representative metaphor, the shared feature is often not one isolable quality; it is a pattern produced by several related elements. Advancing one foot and withdrawing another are separate actions, but their combined opposition provides a vivid model of indecision.
Original scene: opposed movements of bodily advance and retreat.
Intended scene: mental conflict between committing to a decision and holding back.
Shared pattern: instability caused by competing tendencies.
Analyzing each word as an independent trope loses the rhetorical force created by the entire construction.