Farewell, thou child of my right hand, and joy (1)
The speaker says "farewell" to his child, but at this point in the poem we still don't know that the child is dead (the title doesn't say so either). The speaker could be saying "farewell" to his son as he leaves for his first day of school. The speaker initially does everything he can to avoid talking about the death of his son. Art can keep death away…but only for a time.
Seven years thou wert lent to me, and I thee pay,Exacted by thy fate, on the just day. (3-4)
The speaker's metaphor of lending makes death look like something else. The speaker again avoids calling death "death." Instead, he thinks of life and death as some kind of financial arrangement. This makes death seem more fair (the speaker borrowed something and now has to give it back) and somehow less tragic.
[…] For whyWill man lament the state he should envy? (5-6)
The speaker's question implies that death is a good thing, or at least something to envy. He asks why will "man lament," though, not "why will I lament." By making this a universal question, not a personal one, perhaps he's showing that he doesn't necessarily agree with the idea that death is a desirable state.