The death of Rafa
Rafa is a kind of foil to Yunior. Diagnosed with cancer, he sees the brevity of life, and the fear of his imminent death shows Rafa clearly why he should commit to one girlfriend and marry her. It is in light of the challenges of dying and of loss of loved ones that marriage is finally shown to be worth the investment. Instead of having the emotional support of a true spouse, Yunior suffers the loss alone. The death represents the stakes of romance, the ultimate reason to commit to someone.
The motif of transition
The whole novel is set in a state of flux, as seen through this motif. Yunior and Rafa start the novel in a state of adolescence, which is the body's most obvious experience of flux. Their social personalities are being modulated through the stories, as signified by the nine stages of plot, and also, Yunior fails to escape the transitional phase of his own commitment issues, meaning that he suffers the death of his brother alone. The full effect of the motif is to suggest the transitory, ephemeral quality of life.
Nostalgia and adaptation
Yunior suffers from his propensity to be indecisive. Perhaps nothing more plagues him, and it takes everything away from him in the fullness of time. Why should this single character flaw cause Yunior so much agony, failure, and shame? Perhaps the nostalgia and change-aversion that he feels regarding the Dominican Republic might be a clue. If he doesn't want to deal with change in a committed, strategic way, it seems Yunior will be left to suffer a nostalgic nightmare, as if the good times have finally ended and there might never be good times again. This emotion makes Yunior feel trapped, and it makes him less adaptive.
The motif of victimhood
This isn't about "Playing the victim;" in fact, it's the opposite, because Yunior really does make his girlfriends into his real victims, because he betrays their confidence. The girls really like Yunior, but he doesn't really perceive them as people. He uses them as sexual objects, and that isn't really enough of a commitment to prevent him from accepting any new romantic possibilities. He cheats on everyone he dates, and the girls have to cooperate to share the intel around that he is a sexual predator; he lies to women to sleep with them.
Hatred
There are symbolic reminders of hatred as an essential issue in this plot. For instance, Yunior's fate is that he feels he is the victim of severe racism in Boston. Perhaps he really is a victim of hatred, or perhaps Yunior has been socialized in light of the rumors about him, and perhaps he exchanges negative energy with those he speaks with. Without cultivating his respect or love for women, perhaps he is doomed to negative social experiences until he learns empathy. The thematic effect is that in silent ways, Yunior is hateful.
