What words or phrases in this excerpt from "Thanatopsis" by William Cullen Bryant best help to reveal the meaning of the word blight as it is used in the poem?

She has a voice of gladness, and a smile
And eloquence of beauty, and she glides
Into his darker musings, with a mild
And healing sympathy, that steals away
Their sharpness, ere he is aware. When thoughts
Of the last bitter hour come like a blight
Over thy spirit, and sad images
Of the stern agony, and shroud, and pall.
And breathless darkness, and the narrow house,
Make thee to shudder, and grow sick at heart--
Go forth, under the open sky, and list
To Nature's teachings,