I accepted that the Fall had these consequences, but the connection between losing God and losing yourself was never obvious to me. As has been happening regularly in my re-reading of Gilson's The Spirit of Medieval Philosophy, Gilson made clear what should have been obvious all along:
The trouble is that he is himself involved in the mystery. If, in any true sense, man is an image of God, how should he know himself without knowing God? But if it is really of God that he is an image, how should he know himself? There are depths in human nature, unsuspected by the ancients, that make man an unfathomable mystery to himself. (Ch. 7)
Of course. Man is an unfathomable mystery because he is an image of an unfathomable mystery; as long as he in God's grace, and God grants him supernatural of Himself (and therefore that of which man is an image), man may know himself. But when he no longer knows God, he no longer knows that of which he is an image, and so he no longer knows himself.
But his ignorance has a particular cast in light of this analysis. While all beings naturally refer to God as the source of their being, man does so in a special way as an image of God. When he falls, he may no longer know God, but he still knows himself to the extent that he recognizes that he is the image of something. In other words, man is not the creator of his own meaning, and he senses that to know himself means knowing something greater than himself. This is one of the themes of Plato's Republic; the search for the nature of the soul is simultaneously the search for that within which the soul finds its meaning, which for Plato is the city. But as Gilson notes, the true touchstone of human nature is something far more profound than the secular city.