One major problem in reading, or learning through reading, texts of Zen Buddhism out of context is that it can easily give readers all kinds of frustration. Beginning with "finding where to put one's mind", say through reading the Diamond Sutra (金剛經), and ending with a more muddled mind than in the beginning! I want to give alms to improve my karma. You're on "me-illusion" (我相). I want to help significant others, say my mom, so that they are happier. You're on "human-illusion" (人相). I want to teach chi-kung to help others lead a longer and happier life. You're on longevity-illusion (壽者相) I want to go to a monastery and pray to the Buddha asking for help. You're on "Buddha-illusion" (佛相）. In conclusion: these are all good acts, but this is not Buddhist enlightenment and you still don't know where to put your mind or heart. The definitive verse in the Diamond Sutra wrote:
Every perception is illusion
instead of absolute
You are in one with Tathagata (i.e. enlightened), when
you can see illusion out of absolute
So, you may say: should I then understand everything as Emptiness (空), or meditate on Emptiness? You're on Emptiness-illusion (空相)!
As Carl Jung commented on Suzuki's Introduction to Zen Buddhism, this kind of thinking did boggle a more rationalistic western mind - which for all intend and purposes, means the mind of practically every modern man, living in East or West.
A high-school student of average intellect can easily discover the X-illusion trick and can thus frustrate any learned adult who is seeking "Zen-enlightenment" this manner.
The problem is, in Diamond Sutra, we weren't told the daily practice of the Buddha's students seeking for Enlightenment. The essence has been filtered, and, so to speak, crystallized in the Diamond Sutra. As Subhuti doubted (in Chapter 6 of the Sutra) whether future students can be enlightened without the benefit of the Buddha (who was enlightened, highly intelligent, familiar with his students' learning path, with the complete trust of his students, knowing that his students will think hard and try hard on anything he says; the Buddha also has the patience to try repeatedly when a student fails to be enlightened in certain manner, i.e, won't be frustrated, won't give up, in if a student can't be enlightened during this life, there are more lives to come....etc. etc.)
In this era of democratization in our political culture (in the Gulf countries we are now seeing the latest progress), every guru will be queried, tested, and questioned (and for most cases, they should be!) Future enlightenment therefore would not, in the majority of cases for us common folks, come from gurus, not through reading the Diamond Sutra alone, not through meditation alone, and certainly not through endless frustrated X-illusion pounding from folks who got the same intellect of an ordinary high-school student; but from each of us ourselves. From the guru within YOU.