When Lady Macbeth kills herself, Macbeth states, "Life's but a walking shadow, a poor player that struts and frets his hour upon the stage and then is heard no more" (-28). In other words, Macbeth compares his existence to the condition of being a mere ghost. He goes on to compare people to actors who worry about their brief moment in the spotlight only to cease to exist before they realize it is over. The metaphors Shakespeare uses, comparing life to a "walking shadow" and man to "a poor player" emphasize the fleeting nature of life. Shadows are gone as soon as they appear, and actors only assume their character: the people they represent have no true meaning. Here, Macbeth realizes that his pitiful existence, from the moment he decided to kill King Duncan to the moment when his beloved wife killed herself, has been destroyed by his reckless ambition. This directly shows the damaging power of ambition, a major theme of the play. If Macbeth had been content with his previous title, which was prestigious enough, a wealth of tragedy would have been avoided.