give your head a shake

give your head a shake

An imperative to reevaluate one's ideas, behavior, actions, etc., or to begin acting or thinking sensibly. Primarily heard in Canada. You need to give your head a shake if you really think ghosts exist. Give your head a shake, John—no one is going to pay for a service they already get for free.
See also: give, head, shake
Farlex Dictionary of Idioms.
See also:
  • a reality check
  • reality check
  • hindsight is (always) 20/20
  • hindsight
  • 20/20 hindsight
  • twenty-twenty hindsight
  • go hang yourself
  • butt out
  • Butt out!
  • talk some sense into (one)