Martirio translates to "martyrdom" or "torment." It's a strong and dramatic word that evokes intense suffering.
In the song, the singer uses it to describe the profound pain and suffering caused by a past relationship, singing about "todo el martirio que diste a mi vida" (all the torment you gave to my life). This word powerfully conveys the depth of his hurt and his resolve not to return to that painful situation.
Antonio Machín's "No Vuelvo Contigo" is a powerful declaration of a love that's run its course, even if it hurts. The singer is absolutely firm: "no vuelvo contigo" [I'm not coming back to you], no matter what. He says he'd rather spend his life crying than return, even if the moon disappears from the night sky and he lives in a different world. That's some serious commitment to moving on!
He's not swayed by pleas or excuses, even if his former love blames destiny. The reason is clear: "estando contigo mi vida no es vida" [being with you, my life isn't life]. Despite acknowledging that they both still have feelings for each other, and that they both suffer, he knows they'll "nunca seremos felices" [never be happy] together. It's a bittersweet but resolute goodbye, a song about choosing self-preservation over a love that brings more pain than joy.