How do events in Act 3 Scene 4 of 'Macbeth' give the audience an insight into Macbeth's psychological state?

Act 3 Scene 4 of Macbeth marks an acknowledgement of Macbeth's newfound royal authority, as he hosts the first banquet as king. Whilst the audience is presented with a seemingly sane king at the beginning of the scene, news of Fleance's escape deeply troubles the play's protagonist, and he describes himself as 'cabined, cribbed, confined, bound in to saucy doubts and fears.' The use of the adjectives 'cabined' and 'confined' are significant as they imply Macbeth is trapped within his own conscience, unable to escape the guilt he feels for murdering a close friend (Banquo). Much like he begins to disregard his royal obligations, he begins to disregard reality around him and becomes locked in obsessive introspection, unable to return to rational thought by his pleading wife. In lines 129-139, the pronoun 'I' is repeated nine times, conveying his transition into a psychologically isolated state. Whereas Macbeth and Lady Macbeth have previously found strength in each other - committing atrocities as a pair - Macbeth now becomes trapped within his own psychological state, and this foreshadows his eventual tragic (and isolated) downfall.