Psychologists, from Sigmund Freud onwards, have analysed the phenomenon of sexual attraction. The ancient gods had no problems. Both male and female gods had sex with anyone they were attracted to, apparently without inhibition or any semblance of guilt.
Mere mortals are however generally more cautious.
It is true that there are those who live for the moment and overcome by mutual passion, plunge into a relationship without any thought for the future.
Others simply want to serve the object of their infatuation for the rest of their life, without reservation.
There is, however, a third group, whose choice of a partner is initially determined by essentially selfish motivations. Women search for material security and/or physical protection. Men search for a partner who will enhance their perceived worth, because she is attractive or because she can improve his opportunities for social advancement. For this third group, only after the initial selection does the exploration of sexual compatibility and suitability for a long-term commitment take place. Their objectives are often mutually compatible but once again, dictated by the gods of fate there is inherent randomness in the process.
In his description of the Monomyth, Joseph Campbell describes this stage of the Journey as Meeting with the Goddess. The goddess is the ultimate mentor who gives him what he needs to enable him to complete his journey and return to the normal world in possession of new knowledge or enhanced abilities.
If the Goddess is a woman travelling her own journey then, for her, the Hero becomes the Immortal she has been searching for. It is then necessary for the Hero to reciprocate, giving her what she needs to complete her own journey.