The problem of how to compensate the shadow appears on the surface and disappears, and then comes up again, like a log carried along by a muddy river; and there is nobody there to fish out that log and make a good beam of it.
Jung uses the log as a central metaphor for unconscious shadow-contents that repeatedly surface within the flow of psychic life but are lost because no adequately conscious attitude is present to retrieve and transform them into structural or purposive form.
, Nietzsche's Zarathustra: Notes of the Seminar Given in 1934-1939, 1988thesis