The noun composure means the appearance or feeling of calm and the ability to control your feelings.
Synonyms are aplomb, dignity, poise, or self-control.
The word origins in 1600. It comes from compose meaning “consist of” plus –ure. The sense of “tranquility, calmness, composed state of mind” was first recorded in 1660s, from composed meaning “calm”.
It was amazing how she could retain her composure.
He did, however, quickly regained his composure and continued the show.
Maintain your composure, and your performance will be successful.