How does Lady Macbeth try to calm down her husband after he murders Duncan?
In Shakespeare's "Macbeth," when her husband informs her that he has "done the deed," and is upset, Lady Macbeth simply tells him to "Consider it not so deeply" (II,ii,28) as thinking about it "will make us mad" II,ii,34). Her sang froid has already been established in her earlier speeches; however, the dramatic irony of her comment that thinking about the murder will make them mad cannot be lost upon the reader/viewer.
When Macbeth continues she scolds her murderous husband as "Infirm of purpose" (II,ii,52), instructing him,
A little water clears us of this....Be not lost/So poorly in your thoughts."
She then tells Macbeth to dress for bed and "Be not lost/So poorly in your thoughts. (II,ii,72)
But, it appears at this point that Lady Macbeth is the only one without a conscience as Macbeth cannot clear his mind. He ruefully replies,
To know my deed, 'twere best not know myself./Wake Duncan with thy knocking! I would thou couldst! (II,ii,73-74)