The poem opens with the speaker peaceing out on his ladylove. He kisses her and tells her she is not wrong in saying that all his days have been a dream. In fact, before he splits, he outright says that all he sees and seems is but a dream within a dream.
In the next stanza, the speaker's standing on a loud beach, watching golden grains of sand slip through his fingers. In a classic emo moment, he cries out to God, wishing he could hold on to the sand with a tighter grip (why? Who knows). The poem concludes with the speaker unsure about whether or not everything he sees and seems is just a dream within a dream. We know buddy, beach trips are stressful.