Today’s Daily Dharma:
When your mind is trained in self-discipline, even if you are surrounded by hostile forces, your peace of mind will hardly be disturbed. On the other hand, your mental peace and calm can easily be disrupted by your own negative thoughts and emotions. So I repeat, the real enemy is within, not outside. Usually we define our enemy as a person, an external agent, whom we believe is causing harm to us or to someone we hold dear. But such an enemy is relative and impermanent. One moment, the person may act as an enemy; at yet another moment, he or she may become your best friend. This is a truth that we often experience in our own lives. But negative thoughts and emotions, the inner enemy, will always remain the enemy.
The Dalai Lama, "Loving the Enemy" (Summer 2002)