“There are two reasons why man loses contact with the regulating center of his soul. One of them is that some single instinctive drive or emotional image can carry him into a one-sidedness that makes him lose his balance. This also happens to animals; for example, a sexually excited stag will completely forget hunger and security. This one-sidedness and consequent loss of balance are much dreaded by primitives, who call it, "loss of soul." Another threat to the inner balance comes from excessive daydreaming, which in a secret way usually circles around particular complexes. In fact, daydreams arise just because they connect a man with his complexes; at the same time they threaten the concentration and continuity of his consciousness.

The second obstacle is exactly the opposite, and is due to an over-consolidation of ego-consciousness. Although a disciplined consciousness is necessary for the performance of civilized activities (we know what happens if a railway signalman lapses into daydreaming), it has the serious disadvantage that it is apt to block the reception of impulses and messages coming from the center. This is why so many dreams of civilized people are concerned with restoring this receptivity by attempting to correct the attitude of consciousness toward the unconscious center of Self.” 
― C.G. Jung, Man and His Symbols