People say "Get a life" to infer that the person whey are talking to is a loser and incredibly lame. It's an incredibly weak insult used only by those who have the brainpower of a cactus, a deformed catus at that.

"I've never been a lover, I've always been a fighter. It's high time I fight for love instead of the usual crap reasons I fight for, like my own pride" -- A wise guy