Ataraxia
In Ancient Greek philosophy, ataraxia (Greek: ἀταραξία, from ἀ- indicating negation or absence and ταρασσ- tarass- 'to disturb, trouble' with the abstract noun suffix -ία), generally translated as 'unperturbedness', 'imperturbability', 'equanimity', or 'tranquility', is a lucid state of robust equanimity characterized by ongoing freedom from distress and worry. In non-philosophical usage, ataraxia was the ideal mental state for soldiers entering battle.