Mind, body and prana all three are deeply connected. If any one of them become still other two will become still automatically. Body is gross by nature, prana is subtler than body. Mind is more subtle than prana. So sages have decided to do asana siddhi (achieve stillness of body) first. Then they do prana sadhana to win over prana. When body and prana come under control mind automatically comes under control. So when a yogi controls his mind he wins over illusion because mind creates illusion. Yogi can enjoy state beyond mind that is satchitananda.