On losing what we never possessed

What precisely, is symbolic castration? It is the prohibition of incest in the precise sense of the loss of something which the subject never possessed in the first place. Let us imagine a situation in which the subject aims at X (say, a series of pleasurable experiences); the operation of castration does not consist in depriving him of any of these experiences, but adds to the series a purely potential, nonexistent X, with respect to which the actually accessible experiences appear all of a sudden as lacking, not wholly satisfying

The Plague of Fantasies, Slavoj Zizek, Pg 19