The categories of teachings are endless. The entrance doors to the vehicles are innumerable. The words to be explained are extensive. Even if you succeed in memorising millions of volumes of dharma scriptures, unless you are able to practice the essential meaning, you can never be sure that they will help you at the moment of death. And even if your education in studies and reflections is boundless, unless you succeed in being in harmony with the dharma, you will not tame your enemy, negative emotions. Even if you succeed in being the owner of a trillion worlds, unless you can curtail your plans from within with the feeling that nothing more is needed, you will never know contentment. Unless you prepare yourself with the attitude that your death could happen at any time, you cannot achieve the great aim that is surely needed at the time of death.

-- Longchenpa