In illusion one thinks that he can be happy only by fruitive activities, but what actually happens is that one becomes more and more entangled in the network of action and reaction and does not find any solution to the problem of life. There is a nice song in this connection: "Because of a great desire to have all happiness in life, I built this house. But unfortunately the whole scheme has turned to ashes because the house was unexpectedly set on fire."
The law of nature is like that. Everyone tries to become happy by planning in the material world, but the law of nature is so cruel that it sets fire to one's schemes; the fruitive worker is not happy in his schemes, nor is there any satiation of his continuous hankering for happiness.
- Śrīla Prabhupāda, Śrīmad-Bhāgavatam 3.5.2 Purport