Answer:
In this sonnet, the speaker focuses on his own death and the emotions it provokes in young people (his beloved in particular). Aware that the youth will mourn him upon his death, he suggests them not to be sad.
The very structure of the sonnet contributes to the development of the ideas. The structure of this sonnet is that of a typical Shakespearean sonnet - it contains three quatrains and a final couplet. In the first quatrain, the speaker gives his beloved an advice to mourn for as long as the church bell rings - or, in other words, not for too long. In the second quatrain, the speaker points out that it is a better option to forget him completely, if thinking about him would make people dear to him sad. In the third quatrain, he expresses the idea that his name should not be even mentioned while reading the poem. The final couplet serves both as a conclusion to the poem, but also introduces a new idea: the speaker becomes suddenly concerned with what other people, apart from him and his beloved, will think of them after his death:
"Lest the wise world should look into your moan
And mock you with me after I am gone."