Silent night, no thoughts, unforgettable. What do you mean by sighing and blushing?

From "Song of Eternal Sorrow". I still can't think of you in the dead of night, and the last one is that in the world of mortals (or human beings), the appearance is fleeting and the years are in a hurry. Now one is in the sky and the other is on the ground, which is already a different world (one is still beautiful and the other is an aging old man).