When we practice zazen [Zen Meditation] our mind always follows our breathing. When we inhale, the air comes into the inner world. When we exhale, the air goes to the outer world.
The inner world is limitless, and the outer world is also limitless.
We say “inner world” or “outer world,” but actually there is just one whole world. In this limitless world, our throat is like a swinging door. The air comes in and goes out like someone passing through a swinging door. If you think, “I breathe,” the “I” is extra. There is no you to say “I.” What we call “I” is just a swinging door which moves when we inhale and when we exhale. It just moves; that is all.
When your mind is pure and calm enough to follow this movement, there is nothing: no “I,” no world, no mind nor body; just a swinging door.
–Shunryu Suzuki, Zen Mind, Beginner’s Mind