This beautiful song by Cuban singer-songwriter Silvio Rodriguez is about a reluctant departure. The singer knows he's drifting away, even though he doesn't want to: "Aunque no quiero, veo que me alejo" [Although I don't want to, I see that I'm drifting away].
He leaves a message on the mirror and a postscript drawn in a cloud so his love won't forget him. He was followed by demons last night and didn't want to bring them to her door. He escaped them at sunrise and won't leave until she wakes up. He'll be a whisper and a shadow, leaving just two words that she'll know are his, a fading breath of immortal feelings he swore to her.