For the Stoics, the ideal state of mind was tranquility, not the excitable cheer that positive thinkers usually seem to mean when they use the word ‘happiness’. And tranquility was to be achieved not by strenuously chasing after enjoyable experiences, but by cultivating a kind of calm indifference towards one’s circumstances. One way to do this, the Stoics argued, was by turning towards negative emotions and experiences; not shunning them, but examining them closely instead.
Oliver Burkeman, The Antidote
The word “equanimity” comes from the combination of two Latin terms: aequus, meaning “even, level” and animus, meaning “mind” or “spirit.” Equanimity is characterized by the ability to remain calm, composed, open, and non-reactive in the face of challenging or distressing situations.