Identification with the body involves identification with the sex of the body. It therefore implies a free play only for that limited part of the mind which is in tune with the sex of the body. Since the other part of the mind is repressed and latent in the unconscious, there arises in the conscious part a feeling of incompleteness as well as a tendency to restore completeness through attachment to persons of the opposite sex. By getting entangled with the opposite sex, the buried part of the mind that is not in tune with the body seeks some kind of expression through another. From this point of view sexual attraction might be said to be a result of the effort the mind makes to unite with its own unconscious part.
Sex is a manifestation of the ignorant attempt the conscious mind makes to compensate for the fragmentation entailed in identification with the sex of the body. This attempt to compensate for fragmentation is doomed to be futile, however, because it is not only based upon identification with the body but actually accentuates it by setting into opposition the body of the opposite sex and getting entangled with it through attachment and possessiveness.
-Discourses 7th Ed., p325