“As explained in Bhagavad-gita (15.7), manah-shashthanindriyani prakriti-sthani karshati. When the mind and senses are engaged in material activities, one has to continue his material existence and struggle to attain happiness. In each and every life one is engaged in the struggle to become happy. Actually no one in this material world is happy, but the struggle gives a false sense of happiness.” (Shrila Prabhupada, Shrimad Bhagavatam, 4.28.20 Purport)