Furthermore due to purity, there is the clarity of brightness, cheerfulness, one-pointedness, mastery of the five sense organs and fitness to realize the Self.
As Swami Gitananda quite aptly stated: there is no Yoga (or chance for re-union with the Divine Self Within) without the Yamas and Niyamas. Yoga is a step-by-step process. We are purifying our vessels (the body-mind complex) from inertia and dullness (Tamas), and Rajas (activity) to Sattva (the quality of balance, equipoise and brightness). This alchemical process which is facilitated by our Sadhana or concerted Spiritual Practice leads one to a state of natural cheerfulness, arising from the joy of clear awareness that is one-pointed leading to the mastery of the five sense organs instead of being at their mercy and being led and distracted by them. Only then can we reverse the outward focus of the mind and look within for the Light of the True Self to shine and make itself known.
Our physical vehicle is composed of and our mind is influenced by the fluctuations of the 5 great Elements of Earth, Water, Fire, Air and Space. In turn these 5 elements are imbued with the 3 subtle mode of material Nature or Gunas: Tamas (Inertia/Matter), Rajas (Activity/Energy) and Sattva (Light/Consciousness). Yoga is a process of purifying both the physical and subtle body in order to move through the Gunas and eventually transcend them to the state of Nirguna or Consciousness beyond any dualistic distinctions.