If you simply take little trouble to understand Krsna . . . That tapasya is required: to read Krsna’s instruction, Bhagavad-gita, Srimad-Bhagavatam, and try to understand Krsna. Because that tapasya, if you take little painful . . . It is not painful. It is very pleasing. But we avoid it. We think it is painful. ‘Ah! Who is going to read books? We are meant for selling books, not for reading books.’ This is not good. We should read also. That is tapasya. Don’t think that simply our books are meant for selling. No. It is meant for reading also. If we read regularly, at least two hours, three hours, that is tapasya.

From Srila Prabhupada’s lecture, Sri Vrndavana Dhama, October 20th, 1976