One of the major indicators of Macbeth's fear and nervousness is his hallucinations, which more than likely result from his overwhelming sense of guilt and paranoia. In Act II right before Macbeth is supposed to murder Duncan, he lingers in the hall, still weighing the choice before him. As he stands there, feeling extremely nervous and fearful about the task before him, Macbeth sees a vision of a bloody dagger floating in the air before him:
Is this a dagger which I see before me,
The handle toward my hand? Come let me clutch thee. (II.i)
But Macbeth's paranoid delusion of the bloody dagger is not the only manifestation of his fear and guilt. Later after murdering Banquo, Macbeth reels to see a vision of the murdered Banquo sitting at his banquet table in Act 3, Scene 4:
Thou canst not say I did it: never shake
Thy gory locks at me. (III.iv.62-63)
Macbeth becomes visibly upset at the appearance of the bloody specter and fears that one of the other lords has tried to implicate him. Lady Macbeth passes off her husband's rambling as an illness, or a spell, but the fact remains that Macbeth's mental health is crumbling. He clearly struggles with how to cope with the pressure of his guilt. His fear and paranoia are making him delusional.