give 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
   • But give your head a shake, people. Stop pushing for Wi-Fi at campgrounds around B.C. The entire premise of going camping is to escape from the hustle and bustle of our busy lives.2011 August 19, Roxanne Hooper, “Please, keep the wilderness wild”, in The Record, New Westminster, British Columbia