How we cite our quotes:
That time of year thou mayst in me behold,
When yellow leaves, or none, or few, do hang
Upon those boughs which shake against the cold, (1-3)
So, which attitude do you think the speaker prefers: (a) age gracefully, or (b) rage, rage against the dying of the light? Uh, yeah, definitely not option (a). These lines make it clear that the speaker thinks growing old totally stinks, and makes him feel like a tree shaking its barren boughs "against the cold." Don't you think it's interesting that the speaker isn't even clear about how old he is (just look at all that bandying back and forth about how many leaves there are on the tree)? Couldn't this just make his statement in line 3 that much grimmer—i.e. once you're past a certain age, it doesn't really matter, you're just facing down the grim, cold, wintry specter of death anyhow?
Bare ruined choirs, where late the sweet birds sang. (4)
What do you think—could those "sweet birds" stand for some bodacious babes (of unspecified sex) who used to hang on his arm? We think it's possible. That said, perhaps the most notable thing in this line is the word "late," which is an old-fashioned way of saying "lately." By putting this word into the line, the speaker shows his surprise at how quickly old age has caught up with him. It seems like his glory days of living large and loving were only yesterday—and now he's left with the hangover of being, well, old.
In me thou seest the twilight of such day,
As after sunset fadeth in the west, (5-6)
In some ways, the idea behind the imagery in lines 5-6 is similar to that in line 4—because both of them call attention to how recently the speaker was young. Oddly enough, the lingering afterburn of the speaker's youth here (the light that is still left after the sun has set) might be even more depressing than the imagery of the birds in line 4. After all, at least the birds were a pure memory of good times, whereas this leftover sunlight is a weaker, dimmer, more wasted version of what went before. Mortality's a bummer alright.