Equanimity, which is represented as a balance and calmness of spirit, finds its antithesis in the emotion of anger. Someone who is angry has entirely lost the ability to be level-headed, understanding, calm and balanced. On the pH scale of 1-14, 7 represents neutrality between acids and bases, which lie at opposite ends of the scale. If we classify equanimity with a pH of 7, then the pH of anger can be thought of as a 1 - acidic, destructive and sure to cause gastronomical upsets.
We know from extreme cases that serious stress can lead to ulcerations of the stomach - a medically threatening and extremely painful condition if not treated. And what can ulcers cause? Lack of sleep, depression from lack of sleep...it is amazing when the Sages above are detailing "failing of eyes, and a sorrow of mind" that they are predicting this very kind of condition that this kind of lack of equanimity will cause. A "trembling heart", which the Sages also mention, can be caused by such grave upsets in the GI track; I have seen first hand someone think he was having a heart attack when instead it was a similar feeling that was connected to a digestive disorder. While most of the Sages were not doctors, I can be sure of one thing: they understood what the pH of anger and a lack of menucha hanefesh (calmness of spirit) can do to the human body and the mind.
But what can be said about those on the receiving end of such anger and upset? While it is said that the one harboring the anger will be "made to suffer from abdominal troubles...a trembling heart, and failing of eyes, and sorrow of mind", so too can those around us begin to take on those conditions as well. Indeed, our actions and reactions stem from the inside and begin to make their way through our souls, bodies and eventually to the people and environment around us. If instead we nip in the bud the inception of that unsettledness that threatens us, we will find it easier to be further and further away from worry, rage, hysteria and the physical ailments that aim to destroy our health and others.
Forget the Tums. Only a dose of equanimity will do...