"Si Una Vez" (If Once) is a kiss-off song where Luister La Voz takes back every "I love you" he ever said. He flips the power straight away: "Si yo soy el mar y tú un simple barco de papel" (if I'm the sea and you're just a paper boat), so why would she think he is dying to come back? He built her a castle on debt, "me hice deudas pa' crearte un castillo" (I went into debt to build you a castle), and she threw him out anyway, bringing "en vez de amor... un cuchillo" (instead of love, a knife).
The chorus is the whole attitude: "Si una vez dije que te amaba, hoy me arrepiento" (if I once said I loved you, today I regret it). The best line for learners is the last one, "fue sin querer, queriendo" (it was unintentionally, on purpose), a famous Latin American joke phrase from the TV character El Chavo. Also note guayabo, Colombian slang for a hangover: he is drunk, but any hangover is gone by tomorrow. Expect a long list of shout-outs to friends in the middle, too.