noun

calmness and composure, especially in a difficult situation.

she accepted both the good and the bad with equanimity

composure,calmness,calm,level-headedness,self-possession,self-control,even-temperedness,coolness,cool-headedness,presence of mind,serenity,placidity,tranquillity,phlegm,impassivity,imperturbability,unexcitability,equilibrium,poise,self-assurance,assurance,self-confidence,aplomb,sangfroid,nerve,cool,unflappability,ataraxy