This meeting with oneself is, at first, the meeting with one’s own shadow. The shadow is a tight passage, a narrow door, whose painful constriction no one is spared who goes down to the deep well. But one must learn to know oneself in order to know who one is.
For what comes after the door is, surprisingly enough, a boundless expanse full of unprecedented uncertainty, with apparently no inside and no outside, no above and no below, no here and no there, no mine and no thine, no good and no bad.
It is the world of water…..where I am indivisibly this and that; where I experience the other in myself and the other-than-myself experiences me.
The Archetypes and the Collective Unconscious, p. 21

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 interests, so that it is continually subjected to modifications.
But if it is repressed and isolated from consciousness, it never gets corrected.
Psychology and Religion (1938), Collected Works 11, P.131

The shadow is a moral problem that challenges the whole ego-personality…., for no one can become conscious of the shadow without considerable moral effort. To become conscious of It involves recognizing the dark aspects of the personality as present and real. This act is the essential condition for any kind of self-knowledge, and It therefore, as a rule, meets with considerable resistance. Indeed, self-knowledge as a psycho-therapeutic measure frequently requires much painstaking work extending over a long period.
Closer examination of the dark characteristics that is, the inferiorities constituting the shadow reveals that they have an emotional nature, a kind of autonomy, and accordingly an obsessive or, better, possessive quality. Emotion, incidentally, Is not an activity of the individual but something that happens to him. Affects occur usually where adaptation is weakest, and at the same time they reveal the reason for its weakness, namely a certain degree of inferiority and the existence of a lower level of personality. On this lower level with its uncontrolled or scarcely controlled emotions one behaves more or less like a primitive, who is not only the passive victim of his affects but also singularly incapable of moral judgment.
Aion