Are you trying to say you had stopped breathing?
No no, hes saying that his breathing was appearent for the first part of the process and then as he faded into the astral he didn't have to breath on his own anymore, just like in waking conciousness. You breath without being aware of it. When attempting projection, you alter your breathing as needed, and to him, it became second nature and automatic.
Or at least thats how I comprehended it. if im being a smartalec in some way Berry and im wrong, tell me

"View people like a shattered mirrior. The peices show the distorted personality. View the peices as a whole and you will see their true reflection."-Poem by Me