One day, in a talk on various subjects, Dogen said,
Originally, there is no good or evil in the human mind. Good and evil depend on the situation. For example, when we arouse bodhi-mind and enter some mountain or forest, we think that staying in the mountains is good and living in human society is bad. But then, we get bored and leave the mountain thinking it bad. This is because the mind has no fixed characteristics; it changes in various ways depending on the circumstances. Therefore, if you encounter good circumstances, your mind becomes good; if you encounter bad circumstances, your mind becomes bad. Do not think that your mind is bad by nature. Just follow good circumstances.