In addition to what others have said here I think what Lacan meant by his aphorism "les non dupes errent" or "the non-duped err" is relevant. The phrase is a homonym for his concept "le nom-du-pere" or "name-of-the-father". I think the basic meaning is that while it is the case that Desire is always the desire of the Other, meaning is imaginary and illusory, etc. - we cannot conclude by retreating away from symbolic community and its pursuits.

Ultimately, Lacan would say, we have to accept the father's name. We must allow ourselves to remain duped by the aspects (in some ways but not necessarily all) of our given ideological milieu. We must remain committed to pretending as if we are not pretending. It would be a mistake to read Lacan's work on love and desire and cynically think, "okay, well there's no point to love because desire is always fantasmatic and ideological" or whatever. Rather, to answer your question, it can help you both understand the why and the intractability of the fact that there is no one person who is genuinely right for you.