"If you are concentrated on your breathing you will forget yourself, and if you forget yourself you will be concentrated on your breathing. I do not know which is first."
Our respiratory system is part of the involuntary nervous system and also of the voluntary nervous system. Therefore by breathing consciously with awareness we also affect our complete nervous system in a beneficial way. If our awareness is on our breathing there is no place for anything else and thus we experience relief from the hamster cage of our monkey mind.
This is how Shunryu Suzuki speaks of it:
“If you seek for freedom, you cannot find it. Absolute freedom itself is necessary before you can acquire absolute freedom. That is our practice. Our way is not always to go in one direction. Sometimes we go east; sometimes we go west. To go one mile to the west means to go back one mile to the east. Usually if you go one mile to the east it is the opposite of going one mile to the west. But if it is possible to go one mile to the east, that means it is possible to go one mile to the west. This is freedom. Without this freedom you cannot be concentrated on what you do. You may think you are concentrated on something, but before you obtain this freedom, you will have some uneasiness in what you are doing. Because you are bound by some idea of going east or west, your activity is in dichotomy or duality. As long as you are caught by duality you cannot attain absolute freedom, and you cannot concentrate.
Concentration is not to try hard to watch something. In zazen if you try to look at one spot you will be tired in about five minutes. This is not concentration. Concentration means freedom. So your effort should be directed at nothing. You should be concentrated on nothing. In zazen practice we say your mind should be concentrated on your breathing, but the way to keep your mind on your breathing is to forget all about yourself and just to sit and feel your breathing. If you are concentrated on your breathing you will forget yourself, and if you forget yourself you will be concentrated on your breathing. I do not know which is first. So actually there is no need to try too hard to be concentrated on your breathing. Just do as much as you can. If you continue this practice, eventually you will experience the true existence which comes from emptiness.”I like how Shunryu gives us a taste of the playfulness of Zen that may not often be sensed in most of the basic classic Zen texts. "Just do as much as you can." This expresses the Zen attitude that each of us must find our own true way. It cannot be found in any teaching of book. Enjoy!
Source: Shunryu Suzuki, Zen Mind, Beginners Mind, p. 112, 113