Dylan Thomas's poem "Do Not Go Gentle into That Good Night" is a villanelle, meaning that the concluding words are inevitable. The last two lines are the same as the first and third lines of the initial verse:
Do not go gentle into that good night.
Rage, rage against the dying of the light.
The difference is that in the last stanza, the speaker reveals that he is addressing his father. Although the exhortation not to die calmly has been fierce and passionate throughout the poem, it has also been curiously impersonal. Thomas creates the impression that he is stating a universal law that one ought not to accept death, by describing the reaction of various different types of men on their deathbeds. He lists the ways in which wise men, good men, wild men, and grave men rage against death. It is only at the end of the poem that he mentions his father, apostrophizing him directly, and asking for his curse as much as his blessing.
The speaker asks of his father not that he should be forgiving or tranquil but that he should struggle furiously against death. A curse or a display of anger would at least show that he is still alive for the moment, even though his end, like the end of the poem, is inevitable.