18.33 धृत्या by firmness, यया (by) which, धारयते holds, मनःप्राणेन्द्रियक्रियाः the functions of the mind, the Prana and the senses, योगेन by Yoga, अव्यभिचारिण्या unswerving, धृतिः firmness, सा that, पार्थ O Arjuna, सात्त्विकी Sattvic (pure).Commentary: When firmness is awakened in the mind, the activities of the mind, the lifeforce and the senses are brought under control. The senses are withdrawn into the mind. The Prana and the Apana pass into the Sushumna Nadi.Yoga Samadhi or concentration of the mind. You cannot restrain the mind, the lifeforce and the senses by mere firmness. You can control them only by firmness which is ever accompanied by concentration of the mind.When the mind, the lifeforce and the senses are curbed by unwarvering firmness, they cannot run towards external sensual objects, they cannot do any mischief, they cannot move in ways which are opposed to the scriptures, they will be absorbed into their respective causes and their outgoing tendencies will be totally checked.This firmness is not repression or suppression, but an intelligent sublimation and inner transformation.