The Guilt Begins to Show
Right after Macbeth arranges Banquo's murder, we see how differently he and Lady Macbeth are handling the stress. Lady Macbeth delivers one of the play's most famous lines: "What's done is done" - trying to convince herself (and Macbeth) to move on from Duncan's murder.
But she's clearly struggling too. She admits that getting what you want through evil means leaves you feeling empty: "Naught's had, all's spent, where our desire is got without content." This shows she's starting to regret their actions.
Meanwhile, Macbeth is having a complete mental breakdown. He uses the metaphor of a wounded snake to explain that their problems aren't over - they've only made things worse. He's envious of Duncan, who now sleeps peacefully in death whilst Macbeth suffers from constant nightmares.
Quick Insight: Notice how their roles are reversing - Lady Macbeth was the strong manipulator in Act 1, but now she's trying to comfort a paranoid Macbeth.
