This is an excellent passage. Mind is an important component of our existence. According to Yogic philosophy every being consists of five layers: Physical, Vital Air (Prana), Mind, Intelligence and Self (Soul). Prana ( Vital air) is subtle than Physical; Mind is subtle than Intelligence and Self is subtle than intelligence. Yoga basically means the union of all five layers. Yoga starts with physical exercise ( physical poses), Breathing exercise ( Vital Air) followed by Mediattion ( union with Mind) and ultimately Samadhi ( union with self). This also explains why group meditation is so powerful.