Tapo divyaṁ putrakā yena śuddhyed sattva (SB 5.5.1). You must purify your existence. This is the only business of human life: tapasya. So tapasya means brahmacārī. Tapasā brahmacaryeṇa (SB 6.1.13). Tapasya means brahmacaryeṇa, no sex life. That is tapasya, real tapasya. Tapasā brahmacaryeṇa śamena damena ca. Even if you practice yoga system, these regulations must be followed, celibacy, not that fashion yoga system. Now in your country there are so many transcendental yogīs, and they say, "Yes, whatever you like, you can do. God has given you senses. You must enjoy." These are manufactured cheating processes. But actually yoga means indriya-samyamaḥ. Yoga indriya-saṁyamaḥ. Not gymnastic. That is not yoga. Yoga indriya-saṁyamaḥ. Mind control. The same thing, mind control. So mind you cannot control unless your mind is fully engaged in the service of Kṛṣṇa. Sa vai manaḥ kṛṣṇa padāravindayor vacāṁsi vaikuṇṭha-guṇānuvarṇane (SB 9.4.18). These are the examples.
So Raghunātha dāsa Gosvāmī followed very strictly, Caitanya Mahāprabhu also followed very strictly, and the Rūpa-Sanātana Gosvāmī followed very strictly. Not that because one is living in Vṛndāvana with a short cut cloth and therefore he has become like Rūpa Gosvāmī . . . Rūpa Gosvāmī was fully engaged. Nānā-śāstra-vicāraṇaika-nipuṇau sad-dharma-saṁsthāpakau lokānāṁ hita-kāriṇau (Sad-gosvamy -astaka 2). They were in Vṛndāvana, but they were always thinking how to do good to the people, to this material world. Just like Prahlāda Mahārāja: śoce tato vimukha-cetasa (SB 7.9.43). Sādhu's concern is to think of the misled materialistic persons. They are always thinking, making plan how to elevate them, they are suffering. This is sādhu. Lokānāṁ hita-kāriṇau, sādhu, not that "I have changed my dress in such a way, and people out of sentiment will give me roṭī, and I shall eat and sleep." That is not sādhu. Sādhu . . . Bhagavān, Kṛṣṇa, says who is sādhu. Api cet su-durācāro bhajate mām ananya-bhāk sādhur eva sa mantavyaḥ (BG 9.30). That is sādhu. Who has fully dedicated his life for Kṛṣṇa, he is sādhu. Even he has got some bad habits . . . Bad habits? A sādhu cannot have bad habits, because if one is sādhu . . . If in the beginning he has got some bad habit, that will be rectified. Śaṣvad bhavati dharmātmā.