Gather ye rosebuds while ye may, (1)
While "rosebuds" represent opportunities that one should take advantage
of, the speaker's choice of metaphor comes with its own problems. The
fact that roses have thorns suggest that perhaps the speaker isn't as
gung-ho about carpe diem ("seize the day") as he claims to be.
Perhaps while chasing that opportunity, you might get pricked. Maybe
marriage isn't so great after all.
And this same flower that smiles to-day To-morrow will be dying. (3-4)
In Renaissance usage, "dying" was slang for having an orgasm. Dying,
then, could refer here both to death and life, in that an orgasm
suggests procreation (you know, making babies). The poem's emphasis on
death turns out to emphasize life in its turn, both here and in the
images of the setting sun, which we know will rise again.
The glorious lamp of heaven, the sun, The higher he's a-getting, (5-6)
"A-getting" rhymes with "setting" (see below) and emphasizes a strange,
paradoxical proximity between highs ("higher") and lows (setting). The
yoking together of opposites is a feature of other parts of this poem as
well. Think of the equivalence the poem establishes between marrying
and tarrying (via rhyme) in the last stanza, or even the fact that the
sun both rises and sets at the same time. (It sets in one part of the
world while it rises in another.)