Resignaré comes from the verb resignarse, which means "to resign oneself" or "to come to terms with" a difficult situation. It's a powerful word that conveys a sense of reluctant acceptance and deep sadness.
In the song, Christian Nodal sings, "Me resignaré a olvidarte" (I will resign myself to forgetting you). He's not just saying he will forget his love; he's expressing the painful process of forcing himself to accept that it's over, even though he doesn't want to. This word perfectly captures the heartbreaking feeling of letting go of someone you still love.
Christian Nodal's "Adiós Amor" is a powerful anthem for anyone who has had to make the tough decision to leave a relationship that's no longer working. The singer isn't being kicked out; he's the one walking away. He can see the truth in his partner's eyes: "Miro tus ojos y no eres feliz / Y tu mirada no sabe mentir" (I look in your eyes and you're not happy / And your gaze doesn't know how to lie). He realizes there's no point in pretending anymore and decides that if the love is gone, "es mejor partir" (it's better to leave).
This isn't a sudden breakup. He notes that for a while, "nada es igual" (nothing is the same) and she treats him badly. The really painful part is that he still loves her. He even says he could swear to God "cuánto te quise y te quiero / Todavía" (how much I loved you and I love you / Still). But he knows he has to go, and this time "para siempre" (forever). He reminds her that she once called him "El amor de tu vida" (The love of your life), and he believed it. Now, he has to accept the pain and forget her, repeating the simple, final reason: "Porque me fallaste" (Because you failed me).