noun
equanimity
ek-wuh-NIM-uh-tee/ˌekwəˈnɪməti/
Mental calmness and composure in difficult situations.
She handles even the most stressful days with equanimity.

Etymology
The roots describe an “even mind”: a temper that stays level rather than becoming disturbed. This image directly underlies the sense of calm composure, especially under stress.
In context
the absence of Old Friends one can endure with Equanimity but even a momentary separation from anyone to whom one has just been introduced is almost unbearable
More examples
- He accepts criticism with equanimity and looks for ways to improve.
- Her equanimity helps the team stay focused during emergencies.
- I struggle to maintain my equanimity when plans change unexpectedly.
Similar words
- composure
- Emphasizes controlled behavior and appearance, especially during an upsetting moment.
- serenity
- Suggests peacefulness, without necessarily implying a response to difficulty.