The afternoon of the evening's banquet when Lady Macbeth is alone for a moment, she expresses feelings of depression and anxiety, even though plans have been realized and Macbeth now rules Scotland as king:
Nought's had, all's spent,
Where our desire is got without content:
'Tis safer to be that which we destroy
Than by destruction dwell in doubtful joy.
Assailed by doubt and plagued by fear, she takes no satisfaction in their elevation to royalty. When Macbeth enters, however, she expresses none of her feelings to him; instead she tries to alleviate his disturbed emotional state that is quite obvious to her and to help him get himself under control:
Gentle my lord, sleek o'er your rugged looks;
Be bright and jovial among your guests tonight.
When Macbeth speaks of a "deed of dreadful note" to be done, she asks what he is about to do. When he won't tell her, for once she does not impose her will upon him; she lets the matter drop. Perhaps she truly does not want to know. Perhaps she knows enough already of dreadful deeds.
After the banquet, during which Macbeth had reacted in horror at the sight of Banquo's bloody ghost, speaking to the apparition no one else had seen, Lady Macbeth seems even less engaged. When all the guests have departed, she does not question or criticize Macbeth about his bizarre behavior; she, more than anyone, understands his troubled state of mind. Instead she listens without comment as he raves about Macduff, visiting the weird sisters, and to what extent he is "stepped" in blood. When he concludes, she says only that he needs sleep, thus encouraging him to rest his mind.
Lady Macbeth does not appear again in the drama until Act V when she is observed walking, talking, sighing, and wringing her hands in her sleep, reliving past murders. Her anguish is intense; shortly thereafter she commits suicide.
In the beginning, Lady Macbeth had been a strong, aggressive woman in planning Duncan's murder and manipulating Macbeth into carrying it out. She had celebrated her own strength and cruelty. Her behavior, however, before and after the banquet indicates that she is coming undone, struggling with her own fear and subconscious guilt, while also attempting to deal with Macbeth's deterioration. Finally overwhelmed, she ends her life.