3 ideas
In linking posture to breath, the breath initiates and the movement unfolds within the duration of the inhale or exhale, rather than the breath being squeezed into a predetermined movement speed. This makes breath length the governing constraint: you move only as long and as far as the breath allows, which automatically calibrates effort to current capacity.
A yoga practice must be designed around the practitioner's specific age, health, body structure, occupation, and goals rather than fitting the person into a fixed sequence. The same posture can be modified, staged, or substituted so the practice serves where someone actually is, meaning correct practice is defined by appropriateness to the person, not adherence to an ideal form.
The therapeutic value of a posture comes from its intended function — what it asks the spine, breath, or joints to do — not from achieving its photogenic full expression. A modified pose that preserves the function delivers the benefit, while a deep pose that loses the function through compensation does not, so practice should be evaluated by effect rather than appearance.