Yoga is subject to growth and decay. Even samadhi comes and goes. Focus difficult to attain. Once you attain it, very easy to lose again. The remedy for that is apramatta. Paramatta means flickering mind. Apramatta is mindfulness. He carries on with the discussion on meditation next.
Swami Sarvapriyananda teaches the Katha Upanishad, one of India's most revered texts which is also a part of the Vedas. It is a collection of philosophical poems representing a conversation between the sage Naciketas and Yama (god of death). They discuss the nature of Atman, Brahman and Moksha(liberation).