Your girl catches you cheating. (Well, actually she's your fiancée, but hey, in a bit it so won't matter.)
-- Yunior (Year 0)

Importance: This is the first line of the novel. It establishes the inciting incident for the entire story, which is the fiancée's discovery of Yunior's infidelities. The fiancée subsequently breaks up with Yunior, and the remainder of the story follows Yunior's struggles to come to terms with this loss.

You try every trick in the book to keep her.
-- Yunior (Year 0)

Importance: Despite Yunior's infidelities, he appears to harbor sincere love for his fiancée, and when he is in danger of losing her, he desperately attempts to maintain their relationship. However, Yunior fails and must face the consequent challenges caused by his own waywardness.

At first you pretend it don’t matter.
-- Yunior (Year 1)

Importance: It is said that the process of grief often begins with denial, and as conveyed by the above quotation...