Suddenly looking back, that person is in the waning lights. Where did this poem come from? The content of the poem?

This poem came from the Tang Dynasty poet Xin Qiji's "Sapphire Case·Yuan Xi." This poem described how the author missed his lover in the distance at night, reminiscing about the good times in the past, lamenting that time had passed and that his lover had left. The last sentence: " Suddenly, I turn around, but that person is in the waning lights." It expressed the author's disappointment and sorrow, but at the same time, it also hinted that there might be new hope and opportunities in his life. The whole poem was full of emotion and was one of Xin Qiji's representative works.