Analysis of Sonnet XXI: Love Sweetness

Sweet dimness of her loosened hair's downfall
About thy face; her sweet hands round thy head
In gracious fostering union garlanded;
Her tremulous smiles; her glances' sweet recall
Of love; her murmuring sighs memorial;
Her mouth's culled sweetness by thy kisses shed
On cheeks and neck and eyelids, and so led
Back to her mouth which answers there for all:—
What sweeter than these things, except the thing
In lacking which all these would lose their sweet:—
The confident heart's still fervour: the swift beat
And soft subsidence of the spirit's wing,
Then when it feels, in cloud-girt wayfaring,
The breath of kindred plumes against its feet?