No empire can last forever. No one can live forever, for all are mortals. Such is the Law of Nature . In the controlling cycle, each element conquers an element that follows it, but each element is preceded by a conquering element. For instance, water can put out fire, therefore water precedes fire.
Fire can melt metal, therefore fire precedes metal.
Metal in the form of tool can cut down trees, therefore metal precedes wood. Tree roots can penetrate the earth, therefore wool precede the earth. The cycle repeats itself with water controlling fire. This is known as the controlling cycle. Other times the controlling cycle is also known as the destructive cycle.