Bg 18.33

dhṛtyā yayā dhārayate
manaḥ-prāṇendriya-kriyāḥ
yogenāvyabhicāriṇyā
dhṛtiḥ sā pārtha sāttvikī
Synonyms: 
dhṛtyā — determination; yayā — by which; dhārayate — one sustains; manaḥ — of the mind; prāṇa — life; indriya — and senses; kriyāḥ — the activities; yogena — by yoga practice; avyabhicāriṇyā — without any break; dhṛtiḥ — determination; — that; pārtha — O son of Pṛthā; sāttvikī — in the mode of goodness.
Translation: 
O son of Pṛthā, that determination which is unbreakable, which is sustained with steadfastness by yoga practice, and which thus controls the activities of the mind, life and senses is determination in the mode of goodness.
Purport: 

Yoga is a means to understand the Supreme Soul. One who is steadily fixed in the Supreme Soul with determination, concentrating one’s mind, life and sensory activities on the Supreme, engages in Kṛṣṇa consciousness. That sort of determination is in the mode of goodness. The word avyabhicāriṇyā is very significant, for it indicates that persons who are engaged in Kṛṣṇa consciousness are never deviated by any other activity.