These are an explanation from “The Laws of The Sun”.
When you attain the state of arhat, you have the strong faith and unshakable mind with which to withstand worldly troubles. You can receive guidance from your guardian spirit on a daily basis, and you can understand the feelings of others as if you are seeing through their minds. In other words, you have become spiritually mature, and as a religious person, you have reached a level where you can teach and guide people.
Nonetheless, even at this stage, you are still in danger of falling down the ladder of enlightenment. You haven’t grasped the scale, height, and depth of the teachings of Buddha’s Truths, nor have you gained access to the enlightenment of bodhisattvas, which means that you are still at high risk of being misled by disbelief and evil thoughts. If you attune your mind to the spirits that reside in the Tengu Realm and the Sennin Realm in Minor Heaven, you may be tempted by rudimentary spiritual ability that grants you psychic power and the ability to cause spiritual phenomena. Instead of seeking such supernatural powers, however, you should deepen your love and continue your pursuit of higher levels of enlightenment. And never forget the significance of studying the Truths.
One reason people tumble from the state of arhat is that they neglect their efforts to polish their minds. If your mind were made of metal, you would need to remove all the rust and make it shine to attain the state of arhat. Even so, it would get rusty again if you forgot to polish it. If you do not notice that your mind is getting rusty because you’re convinced that you are a great master who has become enlightened, then you are in great danger of falling.
When your mind has been polished to a bright sparkle, its surface is very smooth, which makes it capable of repelling negative energy, no matter how evil such energy may be. But when your mind gets rusty, its surface becomes rough, and all sorts of negative thoughts and ideas stick to it. What’s more, devils in Hell can drive pitons into the receptive surface of your mind and hang ropes that reach down into the depths of Hell. Various creatures, including lost souls, animal souls, and even Satan, can climb up the ropes from the world of darkness and creep into your mind. Some religious leaders, in spite of having managed to reach the state of arhat, allow evil to sneak into their minds this way. This evil confuses them, infiltrates their teaching, and leads them to ruin people’s lives. This is a most dangerous pitfall.
So never forget how vital it is to keep your mind free of rust at all times. Remove the rust and polish your mind until it shines. If you let devils climb into your mind, you’re in deep trouble. As long as you provide access, devils will find the way to creep inside you, no matter how many times you try to exorcise them. You won’t be able to achieve true salvation merely through exorcism or an act of spiritual purification; only a polished mind can protect you from invasions from Hell. This is why maintaining a shining mind is crucial. Studying and practicing the Truths can help you remove the rust and keep your mind polished, and such practice of repelling evil is a prerequisite to higher enlightenment.
So the first step to attaining the higher levels of enlightenment is to reach the state of arhat, which is a pure state of mind undisturbed by worldly matters. In this state, you can communicate with your guardian spirit and sense the feelings and thoughts of others as if they were your own. Until you attain this state of mind, you will not be able to pursue further spiritual training or attain a higher level of enlightenment.