The poet indicates his feeling that he has not long to live through the imagery of the wintry bough, twilight's afterglow, and a fire's dying embers. All the images in this sonnet suggest impending death. In the first quatrain, the poet compares himself to autumn leaves, but he is unable to pinpoint their exact number, just as he cannot determine how close he is to death: "When yellow leaves, or none, or few, do hang / Upon those boughs which shake against the cold." In the second quatrain, he talks of "twilight" as "after the sun fadeth in the west," — a traditional metaphor for death. Death is close to the poet in this second quatrain, for he imagines death twice more, first as "black night" and then as sleep, "Death's second self." The third quatrain recalls Sonnet 45, in which the poet likened his desire for the young man to "purging fire." Now, however, his fire is but dying embers, a "deathbed" fueled by his love for the youth, "Consumed with that which it was nourished by."
Note the pause indicated by the period after each quatrain in the sonnet, the longest pause coming appropriately after the third quatrain, before the concluding couplet. The pauses after the first two quatrains are due to their beginning "In me thou seest. . . ." This phrase indicates that the poet is drawing an allusion between an external image and an internal state of mind, an association that in turn forces a slower reading of the lines, enabling some reflection on the emotional tone that each image evokes.
Now follows the couplet addressed to the youth that makes clear the conclusion to be drawn from the preceding lines: "This thou perceiv'st, which makes thy love more strong, / To love that well, which thou must leave ere long." Believing that he will soon die and never see the young man again, the poet's love for the youth intensifies.