Breathing and Zazen
An important stage in zazen occurs when one stops breathing. Not literally, of course, but when a practitioner stops “doing” his or her breathing, that’s an important stage.

We breathe continually during our lives, both waking and sleeping, and we would perish if we did not. We also breathe automatically, without thinking about it. Just as blood circulates through our arteries and veins automatically, breathing takes place entirely on its own.
However, when a zazen sitter begins the practice, the usual thing is to “do” the breathing himself or herself. That is, the sitter makes a deliberate effort, as slight as it may be, to draw each breath in and to expel it. Let’s call this “doing” one’s own breathing. I don’t know why a practitioner begins this way, but I recall very clearly “doing” my own breathing when I started zazen many years ago.
Alternatively, a zazen practitioner can just “watch” his breathing and not “do” it. Switching to watching the breath can be facilitated by reflecting on the discussion above about the automatic nature of breathing; or it may happen, as in my case, that a sitter takes a breath without consciousness of it and sees that he has done so.
In any event, starting to “watch” the breath instead of “doing” it frees energies in the zazen process to reduce the workings of ego more quickly. So it’s worth trying.