keep a cool head

bang one's head against a brick wall

To waste effort on a futile project.

bash someone's head

To beat up someone violently.

big head

An inflated ego, an exaggerated belief in one's own importance.

bite someone's head off

To severely berate someone.

blow someone's head off

To shoot someone in the head.

bury one's head in the sand

To deliberately ignore the reality of a situation; to pretend a problem does not exist.

cobbler, keep to your last

One should not criticise matters outside one's field of expertise; one should mind one's business.

come to a head

To rapidly reach a turning point or climax.