Why is there first expansion in pranayama and then a return in pratyahara?

According to Osho, expansion in pranayama is followed by return in pratyahara because life thrives as a rhythmic dance of opposites: breath goes out and comes in, creation unfolds and dissolves. Out-breath expands you toward the infinite (fullness); in-breath draws you back to inner emptiness (void). When this polarity stabilizes in awareness, you flow between the two banks—birth and death—and taste the Godlike nature that embraces both.