The word equanimity can be defined as being calm and even tempered. The first time I ever heard it spoken about in an in-depth way was at a Sarah Powers workshop. Powers spoke of equanimity arising from a deep awareness and acceptance of the present moment and this state of being could be evoked through the practice of meditation and yin yoga.
As soon as I heard this concept I felt compelled to chase it down, learn, study, and understand it so I could HAVE it.
Only after reading, pouring through books, did I realize it is not a thought, a feeling, an emotion you can just HAVE. It, like most things, is a practice. There are may ways of finding equanimity through different styles of practice, Buddhism, yoga, martial arts, psychotherapy, can all help us look within and see clearly. What after many years I have come to realize that is true for me, is that equanimity can only be found through self study, through looking at the whole of us, our shadows and lightness. It is the practice of staying present to what is real not our perception, to looking at the ways we create our own suffering and creating change in the areas we can control. It is the practice of knowing ourselves, our triggers, creating boundaries, saying no, pausing before we react, it is about really knowing ourselves.
It is fluid, ever changing, it will not always look and feel the same, it is not something you can control. You will lose your temper, you will not always be calm, you will have emotions you need to feel. How you react is in your control and how you restore your sense of peace is your own person equanimity.
In the yoga sutras 1.33 Patanjali give this advice to keep our mind in a state of well-being:
"Through cultivation of friendliness, compassion, joy, and indifference to pleasure and pain, virtue and vice respectively, the consciousness becomes favorably disposed, serene and benevolent".
B.K.S IYENGAR Light on the Yoga Sutras of Patanjali