Calm emotions while dealing with problems or pressures.
1) He always displays equanimity during his races.
2) She accepted both the good and the bad with equanimity.
Latin aequanimitas, from aequo, animo which means 'with even mind'.
Circa(presumed to be before) 1616
aplomb, calmness, serenity, composure, cool, coolness, countenance
agitation, irritation, discomposure, pertubation.