Pran is the breath that is inhaled,
apan is the breath which moves out.
Sages have found by experience
along with breath
we also imbibe desires from surrounding environment
similarly, transmit waves of inner pious
as well as
Non-assimilation of any desire
from an external source is the offering
pran as oblation,
whereas suppression of all inner desires
the sacrifice of apan,
so that there is generation of
grief because of thoughts of the external world.
So when both pran and apan are properly balanced,
breath is regulated.
This is pranayam, the serenity of breath.
This is the state in which the mind is supreme,
for restraint of breath
restraint of mind.
~Revered Gurudev Swami Adgadanand Jee Paramhans~