The sonnet 73 by William Shakespeare is about the transitoriness of life and love.
The sonnet consists of three quatrains and one couplet at the end.
Shakespeare makes use of the lyrical I to express the content and the feeling which are connected to this subject. .
In the three quatrains there are three prevailing images.
In the first one it is the change of seasons, passing times of the days in the second one and in the last quatrain it is the development from fire to ashes.
In the first quatrain there are symbols which refer to the change of seasons. "When yellow leaves,"."" (l.2) for example symbolizes autumn,.
"cold- and the "bare ruined choirs- (l.3/4) refer to winter and " where late the sweet birds sang- (l.4) stands for spring and summer.
In the second quatrain "sunset-(l.6) refers to evening and "death's second self- (l.8) stands for night. In the last quatrain "glowing- (l.9), "fire- (l.9) and "ashes- (l.10) are part of the prevailing image: a fire which is dying down.
Spring/summer, morning/noon and the fire symbolize youth. You are still active, strong and your soul is carefree and not burdened by many memories of things you have lost in your life. .
Autmn, evening and the glowing of fire refer to becoming/being old.
You lose your beauty and your passion, you are not that active anymore and you have a lot of hurting memories of beloved things and persons you have lost.
Winter, night and the ashes refer to death. Life is over now and you can not change anything anymore.
The couplet at the end has the function of a resume. .
The lyrical I says that you will love "things- more strong by being aware of the fact that you are going to lose within a short time.
Everything is mortal , life and love, and so you must take advantage of them, as long and as well as you can . If you do not do so and you just start loving "things- when you are going to lose it, it might be too late.