"Om Mani Padme Hum

"There is not a single aspect of the eighty-four thousand sections of the Buddha's teachings which is not contained in Avalokiteshvara's six syllable mantra "Om Mani Padme Hum", and as such the qualities of the "mani" are praised again and again in the Sutras and Tantras.... Whether happy or sad, if we take the "mani" as our refuge, Chenrezig will never forsake us, spontaneous devotion will arise in our minds and the Great Vehicle will effortlessly be realized."
Dilgo Khyentse Rinpoche 
-- Heart Treasure of the Enlightened Ones