Do not go gentle into that good night, Old age should burn and rave at close of day; Rage, rage against the dying of the light.
Why it works
This is the poem's opening tercet, and it immediately introduces both refrains: line 1 (A1) and line 3 (A2). Thomas anchors the emotional argument with these two commands right from the start. The iambic pentameter flows smoothly without feeling robotic — "Rage, rage" disrupts the rhythm just enough to evoke the image of a fist slamming on a table. Each following stanza circles back to these lines, and with each return, the sense of desperation intensifies rather than fades.