Two couples of lines carry a small, quiet morning. The speaker has spent hours in bed, talking with his wife until noon, with no hurry and no task pulling them out. The title, "Cocoon," fits: the bed is a warm, closed-off place where the two of them are wrapped in conversation and each other's company.
Then the poem shifts. "Then looking out" opens the view to the world beyond the room, and what the speaker sees is "the new-hung blue." That phrase is the poem's gentle surprise. The sky seems freshly hung, like a curtain or a picture put up just now, as if the day had been prepared while they weren't paying attention. The word "new" also suggests the speaker feels renewed after the long, easy talk.
The mood is contented, calm and a little wondering. Nothing dramatic happens, and that is the point: the poem finds delight in intimacy and in the ordinary sight of a clear sky.