The beloved is more than just a mere human. Her existence is godlike in the fact that she exists when others view her beauty and others get life when they view her beuaty.

The speaker does not want to compare his beloved to solely a summers day because that would make his beloved seasonal. The tone of the poem shifts from summer to spring (darling buds) to fall (summer shall not fade), and winter (death brag).

This makes me think of the narrator being bedridden in old age or sickness and her partner is no longer alive. Since flowers and hospitals also have a close tie like flowers and relationships, the author might be trying to convey how the narrator's relationship with her partner changed over time with old age but still kept the same in some aspects.

The use of "your flowers" instead of just "flowers" insinuates that the partner isn't worried that the narrator doesn't want flowers in general, but, rather, the partner is worried that the narrator wouldn't want flowers from him specifically. This makes me think there has been turmoil in the relationship.