What emotion does the moon reflect in the west window express?

Missing my sweetheart. The bright moon shines in the west window. The extended meaning is that in the dead of night, the moon rises, and the long night of missing your sweetheart brings endless sadness. "West Window" in ancient times meant that it was appropriate to light up the lamp to read at night and cut the candle to talk about love. Cutting candles at the west window originally meant missing the wife far away and looking forward to gathering together to talk at night, but later it generally meant gatherings with relatives and friends. From "The Night Rain Sends to the North". The original sentence is a poem by Li Shangyin of the Tang Dynasty: How can I cut the candles from the west window and talk about the rainy night in Bashan?