Sonnet 73:

THAT time of year thou may’st in me behold
When yellow leaves, or none, or few, do hang
Upon those boughs which shake against the cold,
Bare ruin’d choirs, where late the sweet birds sang.
In me thou see’st the twilight of such day,
As after sunset fadeth in the west,
Which by-and-by black night doth take away,
Death’s second self, that seals up all in rest.
In me thou see’st the glowing of such fire
That on the ashes of his youth doth lie,
As the death-bed whereon it must expire
Consum’d with that which it was nourish’d by.
This thou perceivest, which makes thy love more strong,
To love that well which thou must leave ere long.

(One of the saddest, most beautiful utterances in anybody's literature.)