don't give up the day job

that’s an expression which means someone’s not very good at doing something and isn’t likely ever to be successful at doing it

这是个短语表达的意思是某人并不擅长做事情，并且不会在这方面取得成功。

A: Hey. What do you think of my acting? I'm gonna be a famous actor.

嘿，你觉得我演技咋样?我会成为一个明星!

B: Well, don't give up the day job!

额，别浪费时间了。