Humans are an empathic, compassionate, and loving species, so it is natural to feel sad, worried, or fiery about the troubles and pain of other people. (And about those of cats and dogs and other animals, but I’ll focus on human beings here.)
Long ago, the Buddha spoke of the “first dart” of unavoidable physical pain. Given our hardwired nature as social beings, when those we care about are threatened or suffer, there is another kind of first dart: unavoidable emotional pain.
For example, if you heard about people who go to bed hungry – as a billion of us do each night – of course your heart would be moved. I’m usually a pretty calm guy, but when I visited Haiti, I was in a cold rage at the appalling conditions in which most people there lived. On a lesser scale but still real, a friend’s son has just started college and is calling home to tell his mom how lonely and miserable he feels; of course, she’s worried and upset.