A phrase often used by WWE superstar The Rock (Dwayne Johnson).
It exudes ultimate confidence in yourself;
Telling people you don't give a rat's ass to anybody who wants a piece of you;
In fact you are egging them on to confront/face you.
I don't give a damn if you whine there all day saying how you know what it takes to beat me! I'll be here, waiting.
All you need to do is "JUST BRING IT!"