Nothing is more important than guarding the mind. Let us constantly keep watch over the wild elephant of the mind, curbing it with mindfulness and vigilance. This is how one can avoid being influenced by different external conditions. But even in retreat in a very secluded place, if the mind is not kept under control, it will wander all over the place. Even when completely alone, we can have an enormous amount of negative emotions.
— His Holiness The Dalai Lama, The Path to Tranquility by His Holiness The Dalai Lama, Renuka Singh, editor