Region: US | Usage example: After the critique, he took the bit between his teeth and finished the script.

Take the bit between your teeth

Meaning

Take decisive and energetic action.

Used to describe a determined shift in attitude.

Origin notes can vary by region and source; this page gives the commonly reported explanation and usage context.

Horse training image of a horse grasping the bit and charging ahead.

Western riding metaphor popularized by American riders in the nineteenth century.