It happens only in blink. Sages who have closed there eyes most of there lifetimes than open know when to blink. How much to blink, because blinking has a count. And whosoever blinks is certain, dies.
We live through a series of decision making throughout our days, lets not even go towards a life time, but decisions that we no-one gets to know about. They are our subconscious players that have been leading us our destinies quietly. Like there is only a representative to a vast work that any government does, taking a country forward. Similarly our body being that country is governed by that subconscious mind that is playing its part very softly and one will only reach there once he sits quietly for a prolonged time than less, focusing in the dark to particularly nothing but everything. One by one.
So keep making sure that you sit and sit only, when your stomach is empty. In the times when it needs nothing and has sufficient and energy that it feels good to be there. Only then you can reach out to the foundational breath. To any part that you want to focus on. But know and keep telling yourself as you breathe in, and breathe out that you are not this body. That you are also not the mind.