Macbeth has heard that his wife died but does not realize this as important and meaningless as life is only dust. Tomorrow is a phrase of beats of time that brings with it doom. The candle is maybe the imagery of a soul in which Macbeth's future is grim.
The phrases in this excerpt that help to reveal the meaning of the word "blight" are:
The meaning of the term Blight is <em>scourge, whiter, disaste</em>r.
The support of the meaning in the excerpt is "the last bitter hour": the final moments when someone is going to die.
“stern agony, and shroud, and pall": the end of a life using dramatical terms.
"breathless darkness": a kind of disaster that is coming, not to be avoided that paralyzed people.
