The Moon is a symbol. Of the Mind, of Consciousness, where the dark side references the part outside the light of the mind, that which is a part of the collective unconscious.
The Dark Side of the Moon can also be a symbol of hard work. Hard work and dedication that goes into building something, creating something, discovering something. The achievements are the result of that hard work; it’s the outcome that is visible to the naked eye. The foundation, the building block, the iron frame that made the outcome possible in the first place is hidden, just like the Moon’s unlit side.
As Francis Bacon said, “In order for the light to shine so brightly, the darkness must be present!” Light continues to prevail because darkness, simultaneously, persists to contrast it’s exposure.