When we have suffered, when we fear pain, we empathize with those who are suffering.But when we are suffering, we don't sympathize with others, only with ourselves.But all of us have the possibility of suffering, and can only invest emotions that we don't need at the moment on others.From this it follows that sympathy must be a very pleasurable emotion, which is to our advantage.On the other hand, a man with a heart of stone is always unhappy because his situation does not give him the extra emotion to feel for those who are suffering.