This method of Chan meditation requires that as we meditate, we adopt a down-to-earth attitude. We have to cultivate with our "nose to the grindstone," so to speak. We have to be courageous as we advance. We absolutely may not retreat. With this persevering attitude, we are qualified to be called true Chan meditators.
As we meditate Chan-style, we use patience to overcome all pain. If our legs hurt, we pay no attention. If our back aches, we pay it no mind. If you really want to get enlightened, you have to be patient. If you can't be patient, then you can't get enlightened. The patience that I am talking about includes patience with hunger, patience with thirst, cold, and pain. You have to endure all these different trials. If you can endure them, then you can break through attachment to a self. If you have no attachment to a self, then when you look inside to contemplate your mind, you won't find it. When you look outside to contemplate your body, your body is also gone. When you look afar at all the different things in the universe, none of those things exist either. That's the time when "inside you find no body and mind, and outside you find no world." This is a state of emptiness.
This emptiness, however, is not something to become attached to. If you still hang on to an emptiness, then you are still clinging. Only if you can get rid of emptiness as well, can you become one with, and the same as, the Dharma Realm. You will not be different in any way from empty space. When this state reaches an ultimate point, you'll attain samadhi. Within samadhi, you are not confused and muddled; you are extremely clear and sharp. We call it a state of being "Thus, thus unmoving; understanding, and constantly aware." It's not that when I sit in meditation, I chart out a plan, I have a motive, and I'm greedy for a state to occur. If you have these vain thoughts, you'll be disturbed by demons.
In the Vajra Sutra it says,
All appearances are false.
If you can see all appearances as false,
Then you'll see the Tathagata.
Therefore, people who meditate cannot attach to states, nor do they want to get greedily attached to spiritual powers. As soon as you have an attachment, you can be possessed by a demon. Nor do you want to be greedy for and attach to phony fame and profit. Otherwise, you can easily run afoul of cults, or join the followers of demons, and that's something you should fear to the extreme. Cultivators of Chan should be unattached and free of greed. That's why we say,
When the Buddha comes, slay the Buddha;
When the demons come, slay the demons.
Use your royal Vajra-jeweled sword (wisdom) to slice through everything. Don't crave good states, and even less should you crave bad states. By no means should you crave tiny states and assume that they are signs of spiritual skill. If you do, you will surely go down the wrong road. You must not be careless at all.
During the period of our meditation retreat, you must forget yourself, forget other people, forget about time and space. That is to say, "Sweep out all dharmas. Leave all marks and attachments behind." Don't attach yourself to anything; put everything down. At that time you will be able to enter into states of the Four Dhyana Heavens.