"When the sun sets, heartbroken people are at the end of the world" means that the sunset gradually loses its luster and falls from the west. In the cold night, only lonely travelers wander in distant places. Among them, heartbroken people: people who describe grief to the extreme, here refers to travelers who wander the world and are extremely sad; Tianya: a place far from home.
This poem comes from Tianjingsha Qiu Si written by Ma Zhiyuan in Yuan Dynasty. In order to highlight and strengthen the sad feelings, the author selected ten images that can best reflect the bleak and depressed scenery in autumn and the lonely and melancholy feelings of travelers, and concentrated his feelings in these ten images. Finally, this sentence reveals the theme with a touch of sunshine.