In Act 2, after Lady Macbeth sets up the scene and Macbeth murders King Duncan, the couple respond quite differently to the crime that they have just committed.  Macbeth is really nervous and fearful--he worries that someone heard him kill the king.  He is so nervous in fact that he forgets to leave the knife at the scene and brings it back to the bed chamber with him.  When Lady Macbeth sees how nervous her husband is, she tells him that he must pull himself together and act as if nothing has happened.  She is very strong and confident.  At the end of the scene, someone knocks on the door to the castle, and Macbeth says that he wishes the knocking would waken Duncan from his deathly sleep.  Here, he shows regret while Lady Macbeth appears to be comfortable moving forward.