The source of this sentence was a poem in 'Dream of the Red Chamber', the entire poem was called' Linjiang Fairy·Willow Catch'. The original text was as follows: the courtyard is deep and deep. willow catkins fly up the branches. I dance alone, sing alone, my shadow alone. Fragrance fading, flowers drifting away in the verdant pavilion. the moon sets, crows cry, and frost fills the sky. It was hard to let go. It's hard to get over it. The wild geese return to the season for another year. The meaning of this sentence was that the courtyard was so deep that it was difficult to explore the mystery within. The willow catkins fluttered gently on the branches as if they were about to spread their wings and fly high. Dancing alone, only his shadow accompanied him. The moon fell, crows cried, and frost covered the sky. Feelings were hard to part with, longing was hard to forget. It was another year when Yan returned.