Unfortunately there can be no doubt that man is, on the whole, less good than he imagines himself or wants to be. Everyone carries a shadow, and the less it is embodied in the individual's conscious life, the blacker and denser it is. If an inferiority is conscious, one always has a chance to correct it. Furthermore, it is constantly in contact with other interest, so that it is continually subjected to modifications. But if it is repressed and isolated from consciousness, it never gets corrected, and is liable to burst forth suddenly in a moment of unawareness. At all events, it forms an unconscious snag, thwarting our most well-meant intentions.
We carry our past with us, to wit, the primitive and inferior man with his desires and emotions, and it is only with an enormous effort that we can detach ourselves from this burden. If it comes to a neurosis, we invariably have to deal with a considerably intensified shadow. And if such a person wants to be cured it is necessary to find a way in which his conscious personality and his shadow can live together.
~ C. G. Jung, Psychology and Religion: West and East