The fourth of the divine mind states that the Buddha recommended cultivating is Equanimity (upekkhā).

From the Therigatha:
If your mind becomes firm like a rock
and no longer shakes
In a world where everything is shaking
Your mind will be your greatest friend
and suffering will not come your way.

To have a mind that is our greatest friend – that’s something that most of us want. The mind that doesn’t shake is a description of the mind that is equanimous. (Shaila Catherine, https://www.imsb.org/prev/teachings/equanimity.php)

In a way, equanimity is the combination of the three previous sublime mind states: mettā, compassion, and appreciative joy. When these three are well-developed, equanimity prevails.

The Buddha’s definition of equanimity is not to be confused with indifference or stoicism. It is more like an inflated punching bag with a weight at the bottom. You knock it over and it springs…