Going back and finding out more about what you have already studied always helps a lot. It is like combing your hair: you don’t just comb the ends, but you start from the beginning, from the scalp. So going back again and again is very important, in order to realize the meaning and the purpose of the mahayana, the great path of wakefulness. It makes a thorough job, and you begin to realize the basic geography and logic of the whole situation.
From “Cutting Ego Fixation” in The Profound Treasury of the Ocean of Dharma. Volume Two: The Bodhisattva Path of Wisdom and Compassion by Chögyam Trungpa, page 60