Considering the title the reader can understand that the sonnet is part of a collection. As the most of Shakespearian sonnets this may be dedicated to the fair youth.
The structure is the one of the Elizabethan-Shakespearian sonnet, composed by three quatrains and a rhyming couplet. In the quatrains the poet usually shows three different aspects of a problem, while in the rhyming couplet there is a possible solution.
The rhyme scheme is ABAB CDCD EFEF GG.
The quatrains are composed by a dialogue between the speaking voice and a “thou” (you). In the quatrains the poet presents the problem of his old age, comparing it to natural elements like the autumn, the sunset and the fire (which is dying). The solution proposed is an esortation to love more in the present, and take the problem of the fleetingness of the moment as a motivation to love stronger.