From Lovingkindness by Sharon Salzberg, Chapter 9 ("The Gift of Equanimity"):
To have the radiant calm and unswayed balance of mind that we call equanimity is to be like the earth. All kinds of things are cast upon the earth: beautiful and ugly things, frightful and lovable things, common and extraordinary things. The earth receives it all and quietly sustains its own integrity.
It is a state of peace to be able to accept things as they are. This is to be at home in our own lives. We see that this universe is much too big to hold on to, but it is the perfect size for letting go. Our hearts and minds can become that big, and we can actually let it go. This is the gift of equanimity.