This is a salsa romántica love song that opens by giving in: "Completamente de acuerdo" (completely agreed). The singer is not arguing with his partner. He admits she is right that a lot has happened, "Han pasado muchas cosas" (a lot of things have happened), and that the memories weigh heavy.
The picture he paints of the relationship is pretty bleak. She rations her affection, "Dosificas las caricias" (you ration out the caresses), so a touch becomes a surprise. Love is limping along, "el amor anda en muletas" (love walks on crutches), which is a great image for something that still moves but clearly hurts. Passion is on its way out, "La pasión va de salida" (passion is heading out), routine has set in, and "Algo huele a despedida" (something smells like goodbye). Even resentment gets a job: "el rencor pone las reglas" (resentment sets the rules).
Then the chorus flips it. "Hoy nos gobierna el ayer" (today we are ruled by yesterday), he still has his flaws and mistakes, and he even jokes that she is no mannequin and he was never a heartthrob, "yo un galán nunca he sido" (I have never been a ladies' man). But none of that changes the ending: "Pero deliro por ti" (but I am crazy about you). Delirar literally means to be delirious, so he is saying he is lovesick to the point of fever. A good one for learning how Spanish talks about relationships wearing thin while the feeling hangs on.