Wikipedia informs:

Enantiodromia (Ancient Greek: ἐναντίος, romanized: enantios – “opposite” and δρόμος, dromos – “running course”) is a principle introduced in the West by psychiatrist Carl Jung. In Psychological Types, Jung defines enantiodromia as “the emergence of the unconscious opposite in the course of time.”^[1] It is similar to the principle of equilibrium in the natural world, in that any extreme is opposed by the system in order to restore balance. When things get to their extreme, they turn into their opposite. Jung adds that “this characteristic phenomenon practically always occurs when an extreme, one-sided 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.”