it means " stop obsessing over trivia "
in Cheers, cliff, lolling against the bar, I think, says- " hey Coors ( a lager) spelt backwards is "Srooc"
and the bar tender says - o get a life
Grow a pair - is 'Man up!' - - in typical AB speak - someone is gonna ask: " Man up what?"
In an evg class exam ( v impt ) a student was complaining about the hardness of the seats and I exclaimed " Oh! Girl up!" - and a younger student whispered another: " did you hear what that old aged pensioner said to the other old codger?"