This sentence expresses the feelings of missing and lovesickness through metaphor. Missing is compared to a running horse, which has never stopped since it was separated from the missing person, vividly describing the persistence and intensity of missing. Acacia is compared to catkins spit out by willows, flying around the city, forming a scene full of worries, vividly depicting the shade of Acacia. This sentence is the author's deep affection for parting and missing, and his deep concern for those who miss him.