We shall probably get nearest to the truth if we think of the conscious and personal psyche as resting upon the broad basis of an inherited and universal psychic disposition which is as such unconscious, and that our personal psyche bears the same relation to the collective psyche as the individual to society. But equally, just as the individual is not unique and sepa-rate, but is also a social being, so the human psyche is not a self-contained and wholly individual phenomenon, but also a collective one. And just as certain social functions or instincts are opposed to the interests of single individuals, so the human psyche exhibits certain functions or tendencies which, on account of their collective nature, are opposed to individual needs. The reason for this is that every man is born with a highly differentiated brain and is thus assured of a wide range of possible mental functioning which he has neither acquired ontogenetically nor developed himself. To the degree that hu-man brains are uniformly differentiated, the mental functioning thereby made possible is also collective and universal. This explains the interesting fact that the unconscious processes of the most remotely separated peoples and races show a quite remarkable correspondence, which displays itself, among other things, in the well-authenticated similarity between the themes and forms of autochthonous myths.
— Carl Gustav Jung
Jung is naming something that cuts against every story the modern West tells about the individual. The inherited psychic disposition he describes is not a reservoir you dip into voluntarily — it is already the floor beneath your thinking, the condition of any thought that rises at all. You did not acquire it, and you cannot shed it by becoming sufficiently self-aware. The brain arrives differentiated, and that differentiation runs in the same grooves across every human culture that has ever existed.
What the parallel myths disclose is not merely interesting comparative data. They are evidence that the psyche is already plural before you begin — that whatever you call "my unconscious" is not yours in any proprietary sense. The correspondence between an Inuit cosmology and a Yoruba one and a Greek one cannot be explained by cultural contact. It can only be explained by shared structure, by something that precedes both the cultures and the individuals who carry them.
This matters most when the individual ego is certain it is original — when a particular suffering, a particular longing, a particular dream-figure feels entirely personal, entirely unprecedented. The collective substrate does not erase the personal. It contextualizes it. Your suffering is also the suffering that has been dreamed by humans for as long as there have been humans to dream it — and that changes, quietly but entirely, what it means to live inside it.
Carl Gustav Jung·Two Essays on Analytical Psychology·1953