Mentalizando comes from the verb mentalizar, meaning to mentally prepare or to steel oneself for something. It's a less common, yet very descriptive word that captures a specific emotional and psychological state.
In the song, the singer is anticipating the pain of a breakup and sings, "Para el golpe ya me estoy mentalizando" (I'm already mentally preparing myself for the blow). This word perfectly conveys the active effort of bracing oneself for an emotional impact, making it both interesting and relatable.
This song, "Se Vienen Días Tristes" by Christian Nodal featuring Alfredo Olivas, is all about that gut-wrenching moment when you know a relationship is over, even if nothing has been said directly. The singer can tell just by looking at his partner's face that it's the end, saying, "Tu cara no ocupa subtítulos / Para entender que nos llegó el final" [Your face doesn't need subtitles / To understand that our end has arrived]. He's facing his biggest fear: losing her and seeing someone else take his place.
He knows that a simple "Te amo" [I love you] won't change anything now, and he's bracing himself for the pain. He even jokes, "Perdón si lloro, es que estoy ensayando" [Sorry if I cry, it's just that I'm rehearsing], which is a pretty blunt and funny way to express how much he knows it's going to hurt. Despite his heartbreak, he tells her, "Tú vete tranquila, mi amor / Aquí a ver cómo le hago yo" [You go in peace, my love / Here I'll see how I manage], showing a sad acceptance of the situation.