What does "Ya Se Me Olido Quererte" mean?
In particular the "se" in the phrase?
"Se me olvidó" is a pretty common expression meaning "I forgot". A more literal translation would be "It forgot itself to me." The "se" is reflexive. To me, it seems like this expression is a way of avoiding responsibility for forgetting something--you put the blame of whatever was forgotten.
"Ya se me olvidó quererte" means "I have forgotten to love you."