When we practice [meditation] our mind always follows our breathing. When we inhale, the air comes into our inner world. When we exhale, the air goes out 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.
So when we practice [meditation], all that exists is the movement of the breathing, but we are aware of this movement. You should not be absent-minded. But to be aware of the movement does not mean to be aware of your small self, but rather of your universal nature ... This kind of awareness is very important, because we are usually so one-sided.
Our usual understanding of life is dualistic: you and I, this and that, good and bad. But actually these discriminations are themselves the awareness of the universal existence. "You" means to be aware of the universe in the form of you, and "I" means to be aware of it in the form of I. You and I are just swinging doors. [...]
This moment the swinging door is opening in one direction, and the next moment the swinging door will be opening in the opposite direction.
Moment after moment each one of us repeats this activity. Here there is no idea of time or space. Time and space are one. [...]
When we become truly ourselves, we just become a swinging door, and we are purely independent of, and at the same time, dependent on everything. Without air, we cannot breathe. Each of us is in the midst of myriads of worlds. We are in the center of the world always, moment after moment. So we are completely dependent and independent. If you have this kind of experience, this kind of existence, you have absolute independence; you will not be bothered by anything.
Suzuki Roshi was a world-renowned Zen meditation teacher. Excerpt above from the book Zen Mind, Beginner's Mind.