I noticed in my practice that I was unable to sustain my attention on breath when it became relatively subtle . Is this because my mindfulness is not mature enough to hold on to subtle objects of meditation? What sort of action could help me to overcome this?
There is nothing wrong with losing your focus of the breath, as long as wherever the mind goes, you are aware of that moment. That is, in my view, perfect practice. You are not restricting yourself to the breath or anything. Which is correct! Wherever the mind goes, it goes... you can't control it. So by simply watching where the attention of the mind falls upon, you are fully focused in the moment. Just like watching a butterfly gently landing onto different flowers, being carried by the wind. We have no idea how strong the wind will blow nor do will know in which direction... but, you can still watch the butterfly attentively, as it lands.
But that's just my view. My understanding of correct practice. Metta.
What you have to do is:
- realise your mind has wandered away and bring it back. In doing this not the sensations caused by the your attention has gone to. Sensations arising from thought polifration. Apply efforts not to react with craving and clinging maintaining perfect equanimity. Investigate the Dhamma to see arising and passing, i.e., start of sensations, peaking and passing also dividing and dissecting it until you see what it is made of at the level of Kalapas (subatomic particles)
- until there is breathing there is some more opportunity to calm down the fabrications. Keep looking at it applying sustained and continuous effort. After each in breath reviews if you were with the breath for part breath had stopped (initially a small time like a blink of an eye) and the part that you breathed in. Likewise for the out breath.
- you have to prepare your self to look at sensations. So focus on touch and bodily sensations on the chosen spot. (Step 5 to 8, 2nd triad.)
- Also you have to make your self sensitive to all bodies, in order to see subtlest realities pertaining to phenomena at the level of Kalapa. So exercise of looking at the subtlest breath can help increase your sensitivity. Sustained and continuous effort to maintain the focus can help increase concentration.