Every thought and every emotion can be detected in the breath. When you get agitated, mentally or physically, feel fear, anger or sadness, rhythm of the breath synergises with the emotion. 

Ideally, Breath comes back to its natural state but due to gating; energy, both emotional and physical, stays locked-in in the system and gets accumulated over a period of time. 

 

Unless processed, this energy manifests as aura and is visible to people around.

 

The diaphragm is known to store all of this 'gated' energy. Sine Wave Breathing helps ungating the energy.