In fact, in one sense one could define compassion as the feeling of unbearableness at the sight of other people's suffering, other sentient beings' suffering. And in order to generate that feeling one must first have an appreciation of the seriousness or intensity of another's suffering. So, I think that the more fully one understands suffering, and the various kinds of suffering that we are subject to, the deeper will be one's level of compassion.

— Dalai Lama

from The Art of Happiness