When we prepare for Pranayama we want to settle our body to neutrality, so we put ourselves in the Shavasana following the steps previously described. Only then we are able to calmly watch the breath going in and going out. The breath shows us those parts in the body that are not letting go. So therefore breath and body become instrument for us to let go at the deeper level.
Enlightenment is a state where there is no holding on to anything, it is a state of nothingness. So in our body when we make that freedom to come about, this influences also our energetic system. Pranayama is using the breath as a tool to free everything through the touching of the breath in the trunk. When it becomes free-flowing, this is it.