Get a life is an American English idiom usually intended as a taunt¹. The phrase generally instructs its addressee to go out and make their way in the world, without being supported by outside sources such as parents or benefactors². It may also be directed at someone who is perceived as boring or single-minded like morons³, to suggest they acquire some other, more practical interests or hobbies and get dates, find a job, move to their own house etc.

The phrase is also used against people who are viewed as officious or intermeddling in someone else's affairs. It is another way of saying "Get your own life", or "Stay out of my business."

Note:

Get a life是一个美国俗语，通常带有嘲弄的意味。意思是让对方接触世界，不要单纯依赖外部如父母的资助生活。也可以对头脑比较简单的人说，让他们发展更多兴趣、爱好、约会、找个工作、找到属于自己的房子等。

还有一种用法，可以对好插手别人事情的人说，意思是还是管管你自己吧。也可以说"Get your own life"或 "Stay out of my business."