In this speech, Macbeth is so low that he is simply resigned to what he has just been told: his wife has died, but his first comment on the matter is that "she should have died hereafter"—that is, she would have died at some point anyway. Then, however, he goes on to lament the fact that time seems to "creep" on from one tomorrow to the next, inexorably and yet with seeming monotonous slowness without anything ever really changing. "All our yesterdays," he says—all the days which seem so important to us—are really just a procession of moments in our march towards death. We are all, in the end, "fools" who care about their lives without thinking about how fragile they are.
Macbeth describes human lives as like a "brief candle," no sooner lit than snuffed out. He can see no hope in living anymore, but is almost beyond trying to do anything about it. Life seems like a "shadow" to him, with each person a mere "player" on a stage who is only there long enough to play his turn. Ultimately, while life may be full of huge ups and downs for those living it—"sound and fury"—it actually means nothing and has no ultimate impact on the ongoing passage of time.