The word arrepiento means "I regret" and comes from the important reflexive verb arrepentirse. This word is the emotional turning point of the entire song.
In the powerful chorus, Selena sings, "Si una vez dije que te amaba, hoy me arrepiento," which translates to, "If I once said I loved you, today I regret it." Learning this word is key to understanding the song's message of empowerment and moving on from a past mistake.