In working out instinctual desire to possess mother, leading to inevitable conflict with father, the child forms a personality. From Saussure, Lacan collects the idea that language is determined by difference. So too, is the unconscious. The idea of wholeness is illusory. Individuals are fragmented.
Language conditions our unconscious, conscious minds.
It constructs our sense of self. From birth to around 6 months we live in a world of wishes, images, united with the mother. Self image in flux because we don't yet differentiate. Between age of 6 to 18 months we enter a transitional stage, the mirror stage . We literally or metaphorically begin to see ourselves in the mirror, as a differentiated being.