This poem begins with a reference to "that good night," and we spend most of the poem watching one sunset after another, one nightfall after another. When the sun does appear, it speeds across the sky and out of sight pretty quickly. It's the darkness, not the light, that preoccupies our speaker.
- Line 1: Beginning with this line, we have an extended metaphor in which day represents life, night represents the afterlife or a void, and sunset represents the moment of death. Throughout the poem, entering into the dark, noticing night fall, and the last lingering light of the evening will remind us of how easily – and how inevitably – life slips away from us. The first line is also a refrain in the poem, repeated a total of four times. As if that weren't enough to make you notice it, it's got quite a bit of obvious alliteration of n sounds at the beginning of "not" and "night" and hard g sounds at the beginning of "go" and "good." (Even though "gentle" begins with g, it doesn't count as alliteration here because it's a soft g instead of a hard one.) There are also other n sounds buried in the line, in the middle of "gentle" and "into." All this sound play ties the line together into a tidy package, making the words go together, even though they're full of harsh, hard sounds.
- Lines 1-3: These lines are an apostrophe to the person the speaker is addressing. (We don't find out who it is until the last stanza.)
- Line 3: The repetition of the first word of this line, "rage," emphasizes it with an uncanny doubling. The end of the line is united by the similar vowel sounds in the middle of "dying" and "light," a technique called assonance.
- Lines 10-11: Here the sun's rapid flight across the sky is still part of the extended metaphor in which day represents a life cycle, but the sun also becomes a symbol of all that's beautiful, wonderful, or amazing in the world. The sun stands in for all the amazing things in the world that artists and poets might want to celebrate in their work.