In Act 3, Scene 4, Macbeth imagines he sees the ghost of Banquo occupying his chair at the banquet table. Macbeth reveals his guilt while speaking to the ghost.
In Act 5, Scene 1, Lady Macbeth is walking in her sleep. She is reliving the night when she and her husband murdered King Duncan. She is trying to wash imaginary blood off her hand and off her clothing.
In Act 5, Scene 3, Macbeth is thinking of himself and of his own burden of guilt when he speaks to the doctors the following beautiful lines:
Canst thou not minister to a mind diseased,
Pluck from the memory a rooted sorrow,
Raze out the written troubles of the brain,
And with some sweet oblivious antidote
Cleanse the stuffed bosom of that perilous stuff
Which weighs upon the heart?