What is the origin of the idiom "come full circle" and when to use it?

The origin of the idiom "come full circle" goes back to the ancient Greeks, who believed in the concept of the "anacyclosis," the idea that civilizations and governments go through a cycle of birth, growth, decay, and rebirth. Today, the idiom is commonly used in a variety of contexts, including personal growth, historical events, and cultural trends, to describe a situation where something has returned to its original state or position after a series of changes or developments. The idiom implies that the journey has been completed, and the person or thing has returned to its starting point.