Very similar to
calm yourself, it's what you say to someone who's
acting up, maybe buggin, or in serious danger of
going postal.
For maximum impact, use it as a complete sentence at the end of whatever else you wanted to say.
Paris: You borrowed my new
skinny jeans without asking? I'll claw your
eyeballs out, you thieving skank!
Lindsay: Listen beyotch, they needed breaking in by someone with some actual junk
in the trunk. I'll wash 'em before I return 'em. Relax yourself.