If you want to purify your existence—because you are eternal—then you have to practice this tapasya. Not being carried away by the waves of material nature. No. You have to fight. You're fighting against. That is the . . . but you do not know how to fight. That is tapasya.
So, very simple. Tapasya is not very severe thing. Tapasya means to abide by the orders of the śāstra. Just like a diseased man, his tapasya is to abide by the orders of the physician. The physician says that "You do this; you do not do this." So just like a patient, typhoid patient, he's lying on the bed, the doctor physician has advised, "Don't take any solid food. Take liquid food—barley water, glucose water," this is tapasya. This is tapasya. In order to cure him from the disease he should follow the instruction of the physician if he wants to be cured. Then . . . but if he wants to do anything and everything as he likes, then he'll suffer. So tapasya is required.
So Vedic civilization teaches this human . . . really humanity. Vedic civilization does not teach that you do irresponsible anything and everything, and that is accepted. Nowadays, the so-called Vedāntists and so-called Vedic civilization, they are also advocating, "Yes, you can do whatever you like; there is no restriction." But actually that is not the fact. There is restriction: you should eat like this, you should sleep like this, you should mate like this, you should defend like this. They are required. That is called tapasya: voluntarily accepting for my interest. Tapasā, brahmacarya.