“Foolish men seek after material sense pleasure as a substitute for real happiness, but such foolish men forget that temporary so-called happiness derived from sense pleasures is also enjoyed by the dogs and hogs. No animal, bird or beast is bereft of this sense pleasure. In every species of life, including the human form of life, such happiness is immensely obtainable. The human form of life, however, is not meant for such cheap happiness. The human life is meant for attaining eternal and unlimited happiness by spiritual realization. This spiritual realization is obtained by tapasya, or undergoing voluntarily the path of penance and abstinence from material pleasure.” (Shrila Prabhupada, Shrimad Bhagavatam, 1.3.13 Purport)