Aferrado comes from the verb aferrar, meaning "to grasp" or "to cling to". It's a vivid word used to describe someone who is stubbornly holding onto a person, idea, or feeling, even when it might be better to let go.
In the song, the singer would rather suffer for a few months than "vivir aferrado a tu amor toda la vida" (live clinging to your love his whole life). It perfectly captures that feeling of being emotionally stuck, unable to move on from a past love.
If you are looking for the ultimate breakup track with zero sugarcoating, "2 Veces" by Mexican group Los Plebes del Rancho de Ariel Camacho and Christian Nodal delivers exactly that. The narrator accepts that the relationship is dead, choosing short-term heartbreak over endless agony with "Yo prefiero sufrir un par de meses tu partida / A vivir aferrado a tu amor toda la vida" [I prefer to suffer a couple of months over your departure than to live clinging to your love for all my life]. Instead of begging, he lays down a hard rule: if he walks away, it is forever. He knows you cannot force someone to care, noting bluntly that "eso no se pide" [you don't ask for that].
Even though he admits his bad luck with "pa' mi mala suerte / Me está doliendo perderte" [to my bad luck, it hurts me to lose you], the track hits its peak confidence right at the chorus. He tells his ex to disappear once and for all because "un amor como el mío / Te lo juro en esta vida / No te llegará dos veces" [a love like mine, I swear to you in this life, will not come to you twice]. It is honest, a little bit proud, and gives you great everyday phrases for setting firm boundaries.