Get a life is an idiom and catch phrase that has gained international usage. It is intended as a taunt, to indicate that the person being so addressed is attempting to devote themselves to other people's responsibilities. Sometimes the phrase is used to describe people who are viewed as officious or meddling in the affairs of others. It is another way of saying "get your own life", or "mind your own business".[1]
The phrase has also appeared as a generally more emphatic variant of the taunt "get a job"[2] and implies the addressee needs to go out and make their way in the world, without being supported by outside sources such as parents or benefactors.
It may also be directed at someone who is perceived as boring or single-minded; suggesting they acquire some other, more practical interests or hobbies and get dates, find a job, or move into their own home.
It is also applied to workaholics and others who are perceived as dedicated to their work, but not taking the time to relax or enjoy life.