Without enemies you could not fully engage in the practice of patience — tolerance and forebearance. We need enemies, and should be grateful to them. From the viewpoint of training in altruism, an enemy is really your guru, your teacher; only an enemy can teach you tolerance. An enemy is the greatest teacher of altruism, and for that reason, instead of hating, we must respect him.
— His Holiness The Dalai Lama, How to Expand Love