Equanimity

noun

1. The quality of being calm and even-tempered; composure.
2. Evenness of mind or temper; calmness or firmness, especially under conditions adapted to excite great emotion; a state of resistance to elation, depression, anger, etc.
3. Evenness of mind; that calm temper or firmness of mind which is not easily elated or depressed; patience; calmness; composure.

   "to bear misfortunes with equanimity"

4. The state of being calm, stable and composed, especially under stress.
5. steadiness of mind under stress