In Shakespeare's Macbeth, Act II, scene ii, the turning point arises with regard to the change of positions of Macbeth and Lady Macbeth.
At the start of the play, Macbeth is a great and celebrated warrior. He is strong and self-assured. His wife is a schemer who wants to be queen, nagging her husband to take what he wants, regardless of what he must do to get it. However, after Macbeth murders Duncan, his King, his friend, and his cousin, he is undone. He comes back to their rooms carrying the incriminating daggers. He has heard the king's servants awake and say their prayers, but when they said, "Amen," Macbeth was unable to utter the word. He says:
But wherefore could not I pronounce 'Amen'? / I had most need of blessing, and 'Amen' / Stuck in my throat.
After murdering Duncan, he felt his soul in need of God's comfort, yet not surprisingly, it is not there. Lady Macbeth tries to reason with him. She can sense he is coming unstrung. Macbeth goes on to say he thought he...
"...heard a voice cry 'Sleep no more! Macbeth does murder sleep,' / Sleep that knits up the ravelled sleave of care...Still it cried 'Sleep no more...'
Macbeth believes that because he murdered Duncan in his sleep, Macbeth will no longer be able to enjoy the rest and rejuvenation of sleep anymore.
Lady Macbeth shows that "manly" nature she had prayed for earlier, and disdainfully dresses him down (insults him) for his unmanly behavior, including bringing the daggers with him. He refuses to return to the scene of the murder to put the murder weapons back because he is so mentally affected by the night's events; so Lady Macbeth explains that she will do so and tells him to pull himself together.
When Lady Macbeth returns, she again insults her husband saying her hands are now bloodly as well, but she is not the coward he is. ("I shame to wear a heart so white.") She tells him that if they wash up, they will feel better, but this murder has damaged Macbeth's heart, soul and sense of personal morality. For him, washing the blood away will not help him.
When Macbeth hears the knocking at the gates, he responds, with seeming regret:
Wake Duncan with thy knocking! I would thou couldst.
In other words, he wishes the knocking would wake Duncan—it would mean then that Duncan was still alive.
By the end of this section, Macbeth has become haunted by what he has done, and seemingly weaker, and Lady Macbeth has shown how hard-hearted she is, seemingly much stronger than her husband—at least for now.