Aggression is an obstacle to visual dharma, to hearing and the other sense perceptions, and to understanding reality in its fullest sense. To overcome aggression, some kind of fundamental discipline seems to be absolutely important and necessary. Without any actual practice of sitting meditation to enable us to make friends with ourselves, nothing can be heard or seen to its fullest extent; nothing can be perceived as we would like to perceive it. But slowly and naturally, through our discipline, we gradually begin to branch out into the real world.
From True Perception: The Path of Dharma Art by Chögyam Trungpa, page 73.