Looking into life we notice how it continually moves between contrasts: rise and fall, success and failure, loss and gain, honor and blame. We feel how our heart responds to all this with happiness and sorrow, delight and despair, disappointment and satisfaction, hope and fear. These waves of emotion carry us up and fling us down; and no sooner do we find rest, than we are in the power of a new wave again. How can we expect to get a footing on the crest of the waves? How can we erect the building of our lives in the midst of this ever restless ocean of existence, if not on the Island of Equanimity.
One way to cultivate equanimity is to meditate on impermanence. Whatever is causing us to get exciteable is something that will pass. Remember that and it's easier to stay even.
Remember that the Four Divine Abodes (sometimes called the Four Sublime States) are loving-kindness, compassion, sympathetic joy and equanimity.