nerve

To brace or prepare oneself mentally or emotionally for a difficult task.

"She nerved herself for the interview."

A fibre transmitting impulses between the brain or spinal cord and body parts.

"The dentist hit a nerve."

Steadiness, courage, or confidence to face a difficult or dangerous situation.

"He lost his nerve before the jump."

Shameless boldness or impudence; a lack of respect or good manners.

"She had the nerve to ask for more."