Equanimity (Latin: æquanimitas, having an even mind; aequus even; animus mind/soul) is a state of psychological stability and composure which is undisturbed by experience of or exposure to emotions, pain, or other phenomena that may cause others to lose the balance of their mind. The virtue and value of equanimity is extolled and advocated by a number of major religions and ancient philosophies.
In Buddhism, equanimity (upekkhā, upekṣhā) is one of the four sublime attitudes and is considered:
Neither a thought nor an emotion, it is rather the steady conscious realization of reality's transience. It is the ground for wisdom and freedom and the protector of compassion and love. While some may think of equanimity as dry neutrality or cool aloofness, mature equanimity produces a radiance and warmth of being. The Buddha described a mind filled with equanimity as "abundant, exalted, immeasurable, without hostility and without ill-will."
'I recall once, when my father the Sakyan was working, and I was sitting in the cool shade of a rose-apple tree, then — quite secluded from sensuality, secluded from unskillful mental qualities — I entered & remained in the first Jhana: rapture & pleasure born from seclusion, accompanied by directed thought & evaluation. Could that be the path to Awakening?' Then following on that memory came the realization: 'That is the path to Awakening.'
"So when I had taken solid food and regained strength, then — quite secluded from sensuality, secluded from unskillful mental qualities, I entered & remained in the first Jhana: rapture & pleasure born from seclusion, accompanied by directed thought & evaluation. But the pleasant feeling that arose in this way did not invade my mind or remain. With the stilling of directed thoughts & evaluations, I entered & remained in the second jhana: rapture & pleasure born of concentration, unification of awareness free from directed thought & evaluation — internal assurance. But the pleasant feeling that arose in this way did not invade my mind or remain. With the fading of rapture I remained equanimous, mindful, & alert, and sensed pleasure with the body. I entered & remained in the third jhana, of which the noble ones declare, 'Equanimous & mindful, he has a pleasant abiding.' But the pleasant feeling that arose in this way did not invade my mind or remain. With the abandoning of pleasure & pain — as with the earlier disappearance of elation & distress — I entered & remained in the fourth jhana: purity of equanimity & mindfulness, neither pleasure nor pain. But the pleasant feeling that arose in this way did not invade my mind or remain."
Gotama Buddha