"As long as demons exist in this world, they have their own reason to exist. That reason is completely beyond our human speculation., but demons exist in Buddha's world. So we have to find the realm of buddhas within the realm of demons. In other words, in the realm of pain and suffering, we have to find the realm of peace and harmony. This is religious practice. You cannot find any peace by escaping from human pain and suffering; you have to find peace and harmony right in the midst of human pain. That is the purpose of spiritual life.
The important point is: don't react quickly to pain and suffering with hatred or anger, because that is the cause of human troubles. Deal with demons immediately, but try to deal with them with a calm and peaceful mind, not with hatred or anger. If you become angry, as soon as possible make your mind calm. Be kind. Be compassionate. That is the practice of patience. If you do that, very naturally demons will subdue themselves" - Katagiri Roshi, Each Moment is the Universe.