Even though your practice gradually matures, there are as many potential pitfalls in your practice as there are many hazards in the cliff before withered trees. It is necessary to elucidate them in detail. The pitfalls can be recognized only when you have personally gotten that far. Now is the time to talk about them.
诸子工夫，渐渐纯熟，然枯木岩前错落多，正要细细开示。此中消息，身到方知，吾今则可以言矣。
My school differs from the Zen/Chan school in that it has confirmatory signs for each step of the way. Let us first talk about the differences and then the signs of verification. When you are going to practice this, first see to it that you don’t have much on your mind, so that the mind can be alert and free. Make your mind comfortable and your energy harmonious, then enter into quietude.
吾宗与禅宗不同，有一步一步证验，请先言其差别处，然后再言证验。宗旨将行之际，予作方便，勿多用心，放教活泼泼地，令气和心适，然后入静。
In this quiet state, it is essential to get to know the opening and working of the aperture. Don’t sit inside nothingness or indifference (aka Emptiness of Indifference). As you let go of all entanglements, you become alert and self-composed. But don’t get too concerned about attaining the goal either, nor be too eager about making progress. Those who take it too seriously tend to have this problem. It does not mean that you shouldn’t be dedicated and diligent, but verification/validation shows up between existence and nonexistence. The key is to focus without focus.
静时正要得机得窍，不可坐在无事中里，所谓无记空也。万缘放下之中，惺惺自若也。又不可以意兴承当，凡大认真，即易有此。非言不宜认真，但真消息，在若存若亡之间，以有意无意得之可也。
Now in the midst of alertness, relax. But don’t fall into the ensnaring world, where the five kinds of yin demons take charge. When you are meditating, if your state is closer to dry wood and dead ashes, and lacking the yang energy of growth and creativity, then it means you are ensnared in the world of yin. Your energy is cold, your breathing is coarse, and you have a number of other chilling and withering experiences. If you continue this way for long, you will degenerate.
惺惺不昧之中，放下自若也。又不可堕于蕴界，所谓蕴界者，乃五阴魔用事。如一般入定，而稿木死灰之意多，大地阳春之意少。此则落于阴界，其气冷，其息沉，且有许多寒衰景象，久之便堕木石。
Nor must you be led astray and go along with all objects. This happens if, after you have acquired a quiet state, a train of thoughts with all sorts of loose ends suddenly appears for no reason. You find you cannot turn them away, and you even feel comfortable going along with them. This means the master is enslaved by the servant. If you continue this way for long, you fall into the realm of forms and desires.
又不可随于万缘，如一入静，而无端众绪忽至，欲却之不能，随之反觉顺适，此名主为奴役，久之落于色欲界。
At best one reincarnates as human, at worst one reincarnates into the animal realm. Once you know this, you can seek experiential proofs. For instance, a fox may be able to roam in the great mountains enjoying the wind, the moon, the flowers and fruits, and taking his pleasure in coral trees and jeweled grass. But after three to five hundred years, or thousands of ages, his reward is over and he will be born again into the six states of existence. All of these are wrong paths. Once you know the wrong paths, you can then look for signs of liberation.
上者生人，下者生狸奴中，若狐仙是也。彼在名山中，亦自受用，风月花果，舆树瑶草，三五百年受用去，多至数千岁，然报尽还生诸趣中。此数者，皆差路也。差路既知，然后可求证验。
Buddha Mind 