SIN QUERER QUERIENDO is about trying to forget someone and failing on purpose. The title is a well-known Spanish phrase meaning "without meaning to, but meaning to", the excuse you give for something you sort of did on purpose. Marc Segui opens with a sharp image: "Me di cuenta que estaba hecho de cristal" (I realised I was made of glass) when he broke over her, and he felt "el frío del metal" (the cold of the metal) in his chest though "no te hizo falta ni disparar" (you didn't even need to shoot).
He tells himself to forget her, even locks the door and swallows the key, but "Ni queriendo te olvido" (even wanting to, I can't forget you). "Sé que olvidarte será perder el tiempo" (I know forgetting you would be a waste of time). The second half gets bitter: she kept him "como un perro en perrera" (like a dog in a kennel), and for her he was just "un pasatiempo" (a pastime). Watch the wordplay on parte: "me hiciste parte", "me dejaste a parte", "te llevaste una parte" and "me parte" (it breaks me) all in four lines.