Fair is foul and foul is Fair

"Fair is foul and foul is Fair"

                           This line was said in Shakespearean masterpiece Macbeth. It is said by three evil witches in the Act 1 scene 1. what it means? 

                           For me the line "fair is foul and foul is fair" means the good things will turn to bad or ugly and vice versa. That's what the three ugly witches means. The word "fair" is something good and not different while the word "foul" is something bad ,like foul odor means bad odor. These words contrast each other. 

                          The line of the three witches happened to Macbeth. At the start of the story Macbeth lead the other soldiers to their fight. Macbeth is a good leader. When Macbeth killed Duncan and the thane of Cowdor he took too much power to rule and because of this, his good leadership leads to a tyranny. 

All things change also our attitude and goals in our life.