giving one's head a shake

Verb

give one's head a shake (third-person singular simple present gives one's head a shake, present participle giving one's head a shake, simple past gave one's head a shake, past participle given one's head a shake)

1. (Canada, idiomatic) To reassess the common sense of one's behaviour, ideas, etc.
   • If you're thinking about topping your burger with ketchup, mustard, relish and perhaps a couple of pickle slices, you might want to "give your head a shake."2009 August 20, Joanne Chianello, “New program asks you to pass on the sodium”, in The Windsor Star