When those who follow the pravrtti-marga have enjoyed heavenly sense pleasure, they return to this mortal planet again. Thus, through the Vedic principles, they achieve only flickering happiness. Following the pravrtti-marga, the living entity who desires to be promoted to the higher planetary systems performs sacrifices regularly, and how he goes up and comes down again is described here in Srimad-Bhagavatam, as well as in Bhagavad-gita. It is also said, traigunya-visaya vedah: The Vedas deal mainly with the three modes of material nature. The Vedas, especially three Vedas, namely Sama, Yajur and Rk, vividly describe this process of ascending to the higher planets and returning. But Krsna advises Arjuna, traigunya-visaya veda nistraigunyo bhavarjuna: one has to transcend these three modes of material nature, and then one will be released from the cycle of birth and death. Otherwise, although one may be promoted to a higher planetary system such as Candraloka, one must again come down (ksine punye martya-lokam visanti [Bg. 9.21]). After ones enjoyment due to pious activities is finished, one must return to this planet in rainfall and first take birth as a plant or creeper, which is eaten by various animals, including human beings, and turned to semen. This semen is injected into the female body, and thus the living entity takes birth. Those who return to earth in this way take birth especially in higher families like those of brahmanas.