Desarmar literally means "to disarm" or "to dismantle." However, in a metaphorical sense, especially when used reflexively as desarmarse, it means "to fall apart" emotionally or mentally.
In the song, TINI sings, "Me volveré a desarmar" (I will fall apart again). This powerful phrase conveys a deep sense of vulnerability and emotional collapse, suggesting that if her love leaves, she will completely lose her composure and inner strength. It's a more evocative and less common way to express heartbreak than simply saying "I'll be sad."
Have you ever been in a relationship that you know is bad for you, but you just can't quit? That's the feeling TINI sings about in "Si Tu Te Vas". She's completely aware of the situation, calling herself "loca, adicta al ayer" [crazy, addicted to yesterday] and admitting she knows she'll get hurt: "Tocando el fuego yo me quemaré" [Touching the fire I will get burned]. She sees her partner clearly as a "Falso, brillante" [False, brilliant] person who won't change, and she even has a moment of realization that the relationship was suffocating, singing "Cuando me entregué dejé de respirar" [When I gave myself to you I stopped breathing].
But even with all this clarity, she feels trapped. The chorus is this incredible, contradictory statement. On one hand, she says if he leaves, "Pierdo el sentido, muero de frío" [I lose my mind, I die of cold]. But in the very next breath, she predicts what will happen next: "Si tú te vas / Me volveré a enamorar / Me volveré a desarmar / Una vez más" [If you go / I will fall in love again / I will fall apart again / One more time]. It's a painful cycle she can't seem to escape, and she knows it.