kecid deham imaḿ dhīrāḥ
su-kalpaḿ vayasi sthiram
vidhāya vividhopāyair
atha yuñjanti siddhaye
kecit -- some; deham -- the material body; imam -- this; dhirah -- self-controlled; su-kalpam -- fit; vayasi -- in youth; sthiram -- fixed; vidhaya -- making; vividha -- by various; upayaih -- means; atha -- thus; yunjanti -- they engage; siddhaye -- for the achievement of material perfections.
The process described here is meant to fulfill one's material desires, not to bring one transcendental knowledge. Therefore this process cannot be accepted as devotional service to the Lord, according to Srila Bhaktisiddhanta Sarasvati Thakura. Despite all such mystic perfections, the material body will ultimately die. Actual eternal youth and happiness are available only on the spiritual platform of Krishna consciousness.