Naturalness—natural mind — means a more flexible mind, without sticking to something rigidly. When our mind has perfect freedom from everything, and when our mind is open to everything like a mirror, the mirror does not have any particular image on its face always. So, naturally, it will have various images according to the object. That is naturalness.
Zazen mind, we say, means to stop your thinking. To think is to have some picture of something in terms of long or short, or white or black. That is the thinking mind. So when we start to think, our mind will be dead. When we don’t think, our mind is open to various objects….
The best thing is to have actual practice, to control your thinking mind, and to free your everyday life from thinking mind, and just to use your thinking mind when it is necessary. That is what is important. But how you do it is not just to know this kind of thing. The only way to do it is to have actual power to do it. And the way to obtain this kind of power is[to practice zazen.
– Shunryu Suzuki