Relying Upon a Qualified Teacher
To heal lung, it is important to follow advice from a qualified lama, because each case requires specific advice and treatment. Since a qualified lama is skillful in knowing and healing his own mind and the minds of others, such a teacher can accurately identify the treatment in any given case. The lama is said to be the source of all merits and spiritual realizations, so by following his or her advice you are able to use lung as a way to progress on the path to enlightenment. Following one's lama's advice also serves as a good basis for purifying the negative karma that is producing your lung.
I once heard from Lama Zopa Rinpoche that lung is mainly the result of having disturbed the minds of one's teachers in previous lives. Since disturbing the minds of others is heavy negative karma, creating the cause for your mind to be disturbed, there is no need to talk about how heavy it is to disturb the mind of one's teacher, someone who only wants to benefit us. Although i am not very knowledgeable about Dharma, I can definitely say that by following the advice of my lama, my lung improved considerably. This is due to the lama's kindness and wisdom.
by Ven. Thubten Shakya
(excerpt from Balanced Mind, Balanced Body)