“This age of Kali is not at all suitable for self-realization as was Satya-yuga, the golden age, or Treta- or Dvapara-yugas, the silver and copper ages. For self-realization, the people in Satya-yuga, living a lifetime of a hundred thousand years, were able to perform prolonged meditation. And in Treta-yuga, when the duration of life was ten thousand years, self-realization was attained by performance of great sacrifice. And in the Dvapara-yuga, when the duration of life was one thousand years, self-realization was attained by worship of the Lord.” (Shrila Prabhupada, Shrimad Bhagavatam, 1.1.21 Purport)