So the most difficult thing is always to keep your beginner's mind. There is no need to have a deep understanding of Zen. Even though you read much Zen literature, you must read each sentence with a fresh mind. You should not say, "I know what Zen is," or "I have attained enlightenment." This is also the real secret of the arts: always be a beginner. Be very very careful about this point. If you start to practice zazen, you will begin to appreciate your beginner's mind. It is the secret of Zen practice.