By that which the breath is controlled, the mind is also controlled. And by that which the mind is controlled, the breath is controlled.

This verse expresses the fundamental reciprocity between prāṇa and manas (mind) that is the basis of the entire Haṭha Yoga system.

The formulation is symmetrical and reversible:

• Prāṇāyāma → mental control (the path of Haṭha Yoga)
• Mental control → prāṇa control (the path of Raja Yoga)

Both paths are valid and reinforce each other. Haṭha Yoga offers a more accessible entry point: breath is more tangible than mind.

In practice, this means that:

• When the mind becomes agitated, by regulating the breath one can regain calm
• When the breath is agitated, by focusing the mind one can stabilize prāṇa

This bidirectionality explains why Haṭha Yoga integrates physical practices (āsana, prāṇāyāma) with mental practices (dhyāna, dhāraṇā). They are not separate levels but interconnected aspects of the same unification process.