“Assimilation” in this sense means mutual penetration of conscious and unconscious, and not—as is commonly thought and practised—a one-sided evaluation, interpretation, and de-formation of unconscious contents by the conscious mind.
Jung’s foundational definition insists that true assimilation is a bidirectional encounter between consciousness and the unconscious, explicitly contesting the Freudian reduction of unconscious contents to negative ego-categories.
, Collected Works Volume 16: The Practice of Psychotherapy, 1954thesis