For example, a person who has just been promoted at work might say that they feel "on top of the world." Or, a person who has just finished a difficult race might say that they feel "on top of the world."
The idiom "on top of the world" has been around for centuries. It is believed to have originated in the 16th century when it was used to describe a person who had reached the top of a mountain. The phrase has since been used to describe a variety of achievements, both big and small.
No matter how it is used, the idiom "on top of the world" always conveys a sense of joy, accomplishment, and success.