When I breathe there's a certain time gap after the out breath and before the in breath. I find myself being dull or distracted at that time because there's no breath to notice.
Do I notice the lack of breath? Do I notice not noticing?
What I watch are the feelings of irritation or tension or rushing in my mind, generated in the very beginning and the very end of the gap.
My goal in meditation is to notice how I subconsciously create/maintain emotional tension or inner discord through subconscious grasping some idea, and to stop doing that.
When I see that around start and end of the gap my mind has a character of nervousness, then I know I have something to let go. Once I let go, my breathing winding down to the gap and then restarting again from the gap, feels peaceful and more natural.
So, what I really focus on is letting go and relaxing, until I basically feel perfectly good in the here and now. And the breathing around the gap serves as an indicator of the remaining tension.
As I relax, I keep watching more and more closely, in order to notice even smaller and subtler tensions and nervousnesses. It's like zooming in, more and more, on the precise moments the breath stops and restarts.
Then at some point when I really relax, I don't really care about watching the breath anymore, I watch something else (mind?) -- I don't know how to describe.
Let go of the gap. It is an illusion that is chopping up your breathing. Looking for the gap is like cutting up the goose that laid the golden egg. Looking for the gap traps you into holding your breath, which leads to dullness and drowsiness.
Just as a ball thrown in the air spans an arc of ascent and descent, so too does the breath move in a curve. Instead of following the breath itself, follow the arc of your intention to breath in as it rises to a certain weightlessness that pivots effortlessly to an intention of breathing out. As your meditation deepens, your intention relaxes yet the sense of an arc remains. Just a gossamer thread remains. Follow that.
Don't mind the gap. Mind the breath as a whole.
Take your finger off the trigger. Take your foot off the accelerator.
Just sit but with a quiet still silent mind.
Don't attempt to watch the breathing.
The Buddha did not teach to watch breathing.
The Buddha taught to abandon craving.
Every impulse to watch breathing is craving. When this impulse arises, abandon it, realise it, drop it, let it go.
When you stop trying or craving to watch breath and have a silent mind, Anapanasati (which means 'mindfulness with breathing' rather than 'mindfulness of breathing') can naturally take its natural course. 'Mindfulness' means 'to remember to keep the mind' free from craving.
When the mind stops trying to watch breathing, the mind will be free from the thought of 'trying'. Not trying actually makes the silent mind more clear, more sensitive.
Do we need to make an effort to hear a sound, to smell a smell or to see an object? if not, why does an effort need to be made to know/feel the breathing, when the mind is naturally silent?
How to handle the situation when one does not feel the breath is given below:
Just before the nimitta appears, a lot of yogis encounter difficulties. Mostly they find that the breath becomes very subtle and unclear; they may think the breath has stopped. If this happens, you should keep your awareness where you last noticed the breath, and wait for it there.
A dead person, a foetus in the womb, a drowned person, an unconscious person, a person in the fourth jhāna, a person in the attainment of cessation (nirodha·samāpatti), and a brahmā: only these seven types of person do not breathe. Reflect on the fact that you are not one of them, that you are in reality breathing, and that it is just your mindfulness which is not strong enough for you to be aware of the breath.
When it is subtle, you should not make the breath more obvious, as the effort will cause agitation, and your concentration will not develop. Just be aware of the breath as it is, and if it is not clear, simply wait for it where you last noticed it. You will find that, as you apply your mindfulness and wisdom in this way, the breath will reappear.
Knowing and Seeing (Fourth Revised Edition) by the Pa-Auk Tawya Sayadaw