But why say that desire is never satisfied, as if psychoanalysis had a pessimistic vision with respect to human aspirations?
I can appreciate your reservations. I will answer you by saying that in that place where desire does not attain its goal, I mean where it fails, a positive creation emerges, a creative act takes place. If that is the case, you would wonder, why must desire necessarily fail? Desire will never be satisfied for the simple reason that we speak. Inasmuch as we speak, inasmuch as we are immersed in the symbolic world, inasmuch as we belong to that universe where everything has a thousand-and-one meanings, we will never achieve a complete satisfaction of desire, for from here to the full satisfaction of desire, an infinite field constituted by a thousand-and-one labyrinths, spreads out. Since I speak, it is sufficient that on the path of my desire I advance a saying or posit an act, including the most authentic, to immediately encounter a host of equivocations at the source of every possible misunderstanding. Acts can then be creative, but the purest act or the most accurate word could never avoid the appearance of another act or another word that will divert me from the shortest path to the satisfaction of desire. Once the word is uttered and the act is posited the path toward the satisfaction opens once again. One approaches the goal, one posits an act in life, and yet another path opens. This line of desire exactly reproduces the trajectory of an analysis. It is a path which is not traced in advance, but is opened with each experience. The analytic experience takes place, it is inscribed as a point, and it opens from this point to a new section. We pass through it to another point, beginning a new passage. Considered as the trajectory of a cure, analysis is an expanding path, because once the limit is reached, it moves up one notch. The exact formulation would be: analysis is a limited but infinite path. Limited because it always faces a limit that stops it. And infinite because once reached the limit advances infinitely always further. This is precisely the same logic of displacement that we are able to use to understand both the trajectory of desire and the trajectory of an analysis.
According to the set theory proposed by Cantor, this expanding movement is ruled by a principle called the principle of passing to the limit.1 For Cantor, the passage to the limit signifies that arriving at the limit generates an infinite set. And if we return to our terminology, we say that one reaches the threshold, and right away, an additional sequence opens up onto infinity. (36-37)
 Georg Cantor, “Fondements d’une théorie générale des ensembles,” in Cahiers pour l’analyse (Paris: Seuil, 1969), 35-52.
Nasio, Juan-David. Five Lessons on the Psychoanalytic Theory of Jacques Lacan. Trans. Pettigrew, David and François Raffoul. State University of New York Press 1998.
Works and Days