It is said that yogīs always think of the Supreme Personality of Godhead within their hearts. Dhyānāvasthita-tad-gatena manasā paśyanti yaṁ yoginaḥ (SB 12.13.1). The Supreme Personality of Godhead is always observed by yogīs who practice controlling the venomous senses. As recommended in Bhagavad-gītā, yogīs should practice samprekṣya nāsikāgram, keeping their eyes half-open. If the eyes are closed completely, there will be a tendency to sleep. So-called yogīs sometimes practice a fashionable form of yoga by closing their eyes and meditating, but we have actually seen such so-called yogīs sleeping and snoring while meditating. This is not the practice of yoga. To actually practice yoga, one should keep his eyes half-open and gaze at the tip of his nose.
Although Āgnīdhra, the son of Priyavrata, was practicing mystic yoga and trying to control his senses, the tinkling sound of Pūrvacitti's ankle bells disturbed his practice. Yoga indriya-saṁyamaḥ: actual yoga practice means controlling the senses. One must practice mystic yoga, to control the senses, but the sense control of a devotee who fully engages in the service of the Lord with his purified senses (hṛṣīkeṇa hṛṣīkeśa-sevanam (CC Madhya 19.170)) can never be disturbed. Śrīla Prabodhānanda Sarasvatī therefore stated, durdāntendriya-kāla-sarpa-paṭalī protkhāta-daṁṣṭra-yate (Caitanya-candrāmṛta 5). The practice of yoga is undoubtedly good because it controls the senses, which are like venomous serpents. When one engages in devotional service, however, completely employing all the activities of the senses in the service of the Lord, the venomous quality of the senses is completely nullified. It is explained that a serpent is to be feared because of its poison fangs, but if those fangs are broken. the serpent, although it seems fearsome, is not at all dangerous. Devotees, therefore, may see hundreds and thousands of beautiful women with fascinating bodily movements and gestures but not be allured, whereas such women would make ordinary yogīs fall. Even the advanced yogī Viśvāmitra broke his mystic practice to unite with Menakā and beget a child known as Śakuntalā. The practice of mystic yoga, therefore, is not sufficiently strong to control the senses. Another example is Prince Āgnīdhra, whose attention was drawn to the movements of Pūrvacitti, the Apsarā, simply because he heard the tinkling of her ankle bells. In the same way that Viśvāmitra Muni was attracted by the tinkling bangles of Menakā, Prince Āgnīdhra, upon hearing the tinkling bangles of Pūrvacitti, immediately opened his eyes to see her beautiful movements as she walked. The prince was also very handsome. As described herein, his eyes were just like the buds of lotus flowers. As he opened his lotuslike eyes, he could immediately see that the Apsarā was present by his side.