give one's head a shake

Meanings:

• 1.

  GeneralNeutralLiteral
  • To move one's head sharply from side to side, typically as a physical gesture of disbelief, disapproval, or to clear one's thoughts.

• 2.

  CanadaIdiomatic
  • To re-evaluate one's behavior, ideas, or decisions; to abandon unreasonable thoughts and regain common sense.