The darkness which clings to every personality is the door into the unconscious and the gateway of dreams, from which those two twilight figures, the shadow and the anima, step into our nightly visions or, remaining invisible, take possession of our ego-consciousness.
Carl JungI use [Heraclitus' discovery of] enantiodromia for the emergence of the unconscious opposite in the course of time. This characteristic phenomenon practically always occurs when an extreme, onesided tendency dominates conscious life; in time an equally powerful counterposition is built up, which first inhibits the conscious performance and subsequently breaks through the conscious control.
Carl Jung