The dual process of breathing in and breathing out appears to be like a dalliance of Shri Radha Krishna. In other words, Lord Krishna represents vitality (praan) while Shri Radha is the vital air (praan vaayu). Praan cannot survive without praan vaayu, while praan vaayu has no existence without praan. This practice of observing their exclusive union inside us is called 'e-saadhna'.