Tapasya means to undergo voluntarily some inconveniences of this body. Because we are accustomed to enjoy bodily senses, and tapasya means voluntarily to give up the idea of sense gratification. That is tapasya. Tapasya. Just like Ekādaśī. Ekādaśī, one day fasting, fortnight. That is also tapasya. Or fasting in some other auspicious day. That tapasya is good, even for health, and what to speak of advancing in Kṛṣṇa consciousness. So we should accept this tapasya. The upavāsa. There are many prescribed days for fasting. We should observe. And the preliminary tapasya, no illicit sex, no gambling, no intoxication, no..., no meat-eating... There may be some inconvenience, those who were accustomed to this practice, but we'll have to accept. Tapo divyaṁ putrakā yena śuddhyet sattvam (SB 5.5.1). If we want to purify our existence... At the present moment our existence is not purified, impure. Therefore we are suffering. Just like when one's physiological condition becomes infected, he suffers from fever and other symptoms of disease, similarly, we are suffering in this material world on account of this material body. If we want really happiness, then we must accept tapasya. Tapasya is required. Without tapasya, if you think that very easily... Or "Without tapasya, I can get it simply by imagination," then you become sahajiyā, to take things very easily. No. Tapasya.
Therefore Kṛṣṇa says that tapaś cāsmi tapasviṣu. That acceptance of tapasya means that tapasya is itself Kṛṣṇa. You associate with Kṛṣṇa. When you voluntarily give up meat-eating or intoxication, this giving-up, this process, is Kṛṣṇa. Kṛṣṇa says, tapaś cāsmi tapasviṣu. This is tapasya. Tapasya means to accept voluntarily something as enjoined in the śāstras. Śāstra says... Kṛṣṇa says. Whatever Kṛṣṇa says, that is śāstra. What is Veda? Veda means what Kṛṣṇa says; that is Veda. There is no other Veda. Just like in the Śrīmad-Bhāgavatam it is said, tene brahma hṛdā. Brahmā hṛdā. Brahma means Veda. Brahma, śabda-brahma. So Kṛṣṇa tene, imparted, injected brahma, Vedic, Vedic śabda, śabda-brahma, Vedas, tene brahma hṛdā, through the heart. Kṛṣṇa is situated in everyone's heart. So Brahmā had no other spiritual master, but Kṛṣṇa is there within the heart. Therefore Kṛṣṇa's name is Caitya-guru. Buddhi-yogaṁ dadāmi tam. The caitya-guru, the guru... Kṛṣṇa is so kind. He is guru within, and when we are serious, He manifests Himself as a spiritual master. This is described in the Caitanya-caritāmṛta.
So guru is helping from inside and from outside. Antar-bahiḥ. So Kṛṣṇa is so kind. Therefore Kṛṣṇa manifests Himself as spiritual master. Therefore Viśvanātha Cakravartī Ṭhākura says, sākṣād-dhari, sākṣād-dharitvena samasta-śāstraiḥ. Manifestation of empowered. One who is pure devotee, he's empowered by Kṛṣṇa to act as spiritual master. Therefore spiritual master should be accepted: sākṣād-dharitvena samasta-śāstrair uktaḥ **. It is described there. Tathā bhāvyata eva sadbhiḥ. Those who are learned scholars, actual devotees, they accept. But that does not mean guru is Kṛṣṇa. Kintu prabhor yaḥ priya eva tasya. Now, that, if you accept, you... Accept means you honor spiritual master as good as Kṛṣṇa, because he's representative. But not that Māyāvāda philosophy that guru and Kṛṣṇa is the same. This is simultaneously one and different. Kintu prabhor yaḥ priya eva tasya. He is as good as Kṛṣṇa because he is very, very dear to Kṛṣṇa. Why dear? Because he's preaching on behalf of Kṛṣṇa. What Kṛṣṇa wants, he's doing that. Therefore he's very dear.
Kṛṣṇa wants everyone, sarva-dharmān parityajya mām ekaṁ śaraṇaṁ vraja (BG 18.66). A guru's business is that. Guru does not mean that he takes the position of Kṛṣṇa. He simply teaches people that "You accept Kṛṣṇa the Supreme Personality of Godhead. You surrender unto Him. You always think of Him. You always offer your obeisances. You become a pure devotee of Kṛṣṇa." This is guru's business. It is not very difficult. Anyone who is sincerely following Kṛṣṇa's instruction and instructing others also to do that, that is ācārya. Āpani ācari prabhu jīvere śikhāya. This is ācārya. You behave yourself exactly as it is stated in the śāstra, as it is ordered by Caitanya Mahāprabhu, as it is ordered by Kṛṣṇa... Āpani ācari jīvere śikhāya. And you teach all your disciples, who comes to you as your disciples, teach them. This is ācārya.
So ācārya, guru, representative, it is not difficult. Simply one has to become very, very sincere. One must undergo the simple tapasyas as prescribed in the śāstras. Caitanya Mahā... Yes. Haridāsa Ṭhākura. Āpani ācari prabhu jīvere śikhāya. He was preaching also the glorification of chanting Hare Kṛṣṇa by personal example; therefore he is accepted as guru. All the Vaiṣṇavas, all the ācāryas, Gosvāmīs, they acted accordingly and preached. Therefore they are ācāryas. And Kṛṣṇa says, ācāryaṁ māṁ vijānīyān nāva-manyeta karhicit (SB 11.17.27). These are the instructions.