Macbeth's ambition is what causes his downfall. His greed and need for power lead him to murder, manipulate, and deceive. Because of Macbeth's attempts at "preserving" himself, he becomes insance, suffers from hallucinations, and sleeplessness. His madness creates suspicion around him, like when he sees the ghost of Banquo. Macbeth's techniques for self-preservation creates mistrust and turmoil. He in turn, without realizing it, crafts his own doom. The downfall of Macbeth was from Macbeth's own actions. If he had never thought that he should be king in the first place, he never would have been killed. I hope this helps some.