Meanwhile, the speaker is weeping. Just to make sure we get the message, he tells us twice that he is weeping while the sand slips through his fingers.
If holding onto the sand is his way of connecting to reality—to something physical—then it makes sense that he's feeling bummed. His grip on reality, like the sand, is slipping away. That causes him a lot of frustration (note the two exclamation points and all that weeping).
O God! can I not grasp Them with a tighter clasp? O God! can I not save One from the pitiless wave?
As if we didn't already know, the speaker drives home the point about his exasperation (two more exclamation points).
He appeals to God, and asks if he can't hold on to them (the grains of sand) with a "tighter clasp" and if he can't save one from the "pitiless wave."
The negative questions here imply negative answers. The answers to the speaker's "can I not" are clearly meant to be "no, you can't."
The speaker so desperately wants to "save" the sands and hold them "tighter" because he wants to prove that he can do it, to prove that everything is real and not just a fleeting illusion.
The "pitiless wave" harkens back to that roaring, tormenting surf, and makes us think of some type of unforgiving monster. Here, it seems to symbolize the power of illusion or fantasy that keeps defeating the speaker's attempts to convince himself that what is in front of him is real and can be "grasped."
But there's another way to think about all this: dreams end when we wake up, the sand is running away from the speaker, and the speaker leaves a woman behind at the beginning.
Hmm. It kind of sounds like this poem has a lot to say about things disappearing from one's life. Life is a dream, perhaps, because things are always going away: women, reality, people we know, and the like. Nothing lasts, and when we look back on those things, it feels like a dream.
Check out the symmetry of these lines. The first and third lines in the group are almost identical ("Oh God! can I not"). The repetition indicates the speaker's continued failure to succeed in his endeavor.
Is all that we see or seem But a dream within a dream?
Despite his failures, the speaker apparently does not give up hope. Earlier, he had straight up said all that we see and seem is just a dream within a dream.
Here in the poem's concluding lines, which repeat the refrain, the speaker phrases it as a question.
Then again, maybe he's just getting a bit desperate and having a "say it ain't so!" moment.
Even after all the sand has run through his fingers, and even after all his weeping, the speaker can't bring himself to declare that all that we see and seem is but a dream within a dream.
Perhaps he doesn't want to acknowledge the loss of the things in life that have slipped through his fingers—the sand, his ladylove. Maybe he's afraid that none of it was real in the first place. Either way, he's not exactly pumped about life at this moment.
This second stanza looks a lot like the first. It's chock full of rhyming couplets, with a trio tossed in there (in lines 16-18). Only this time, the trio's smack dab in the middle of the stanza, rather than at the beginning, and the second stanza has an extra two lines tacked on. Be sure to check out "Form and Meter" for more.