Định Nghĩa và Ý Nghĩa của "{not} [give] up the day job"

What is the origin of the idiom "not give up the day job" and when to use it?

The origin of the idiom "not give up the day job" is unclear, but it has been in use since at least the mid-20th century. This phrase is used to suggest that someone's performance in a particular activity is not good enough to pursue as a career.