The fundamental philosophical principle of Buddhism is that all our suffering comes about as a result of an undisciplined mind, and this untamed mind itself comes about because of ignorance and negative emotions. For the Buddhist practitioner then, regardless of whether he or she follows the approach of the Fundamental Vehicle, Mahayana or Vajrayana, negative emotions are always the true enemy, a factor that has to be overcome and eliminated. And it is only by applying methods for training the mind that these negative emotions can be dispelled and eliminated. This is why in Buddhist writings and teachings we find such an extensive explanation of the mind and its different processes and functions. Since these negative emotions are states of mind, the method or technique for overcoming them must be developed from within. There is no alternative. They cannot be
removed by some external technique, like a surgical operation."
from 'Dzogchen: The Heart Essence of the Great Perfection'