SB 7.6.5

tato yateta kuśalaḥ
 kṣemāya bhavam āśritaḥ
śarīraṁ pauruṣaṁ yāvan
 na vipadyeta puṣkalam
Synonyms: 
tataḥ — therefore; yateta — should endeavor; kuśalaḥ — an intelligent man interested in the ultimate goal of life; kṣemāya — for the real benefit of life, or for liberation from material bondage; bhavam āśritaḥ — who is in material existence; śarīram — the body; pauruṣam — human; yāvat — as long as; na — not; vipadyeta — fails; puṣkalam — stout and strong.
Translation: 
Therefore, while in material existence [bhavam āśritaḥ], a person fully competent to distinguish wrong from right must endeavor to achieve the highest goal of life as long as the body is stout and strong and is not embarrassed by dwindling.
Purport: 

As stated by Prahlāda Mahārāja at the beginning of this chapter, kaumāra ācaret prājñaḥ. The word prājña refers to one who is experienced and who can distinguish right from wrong. Such a person should not waste his energy and valuable human lifetime simply working like a cat or dog to develop his economic condition.

For one word in this verse there are two readings — bhavam āśritaḥ and bhayam āśritaḥ — but accepting the meaning of either of them will bring one to the same conclusion. Bhayam āśritaḥ indicates that the materialistic way of life is always fearful because at every step there is danger. Materialistic life is full of anxieties and fear (bhayam). Similarly, accepting the reading bhavam āśritaḥ, the word bhavam refers to unnecessary trouble and problems. For want of Kṛṣṇa consciousness, one is put into bhavam, being perpetually embarrassed by birth, death, old age and disease. Thus one is surely full of anxieties.

Human society should be divided into a social system of brāhmaṇas, kṣatriyas, vaiśyas and śūdras, but everyone can engage in devotional service. If one wants to live without devotional service, his status as a brāhmaṇa, kṣatriya, vaiśya or śūdra certainly has no meaning. It is said, sthānād bhraṣṭāḥ patanty adhaḥ: whether one is in a higher or lower division, one certainly falls down for want of Kṛṣṇa consciousness. A sane man, therefore, is always fearful of falling from his position. This is a regulative principle. One should not fall from his exalted position. The highest goal of life can be achieved as long as one’s body is stout and strong. We should therefore live in such a way that we keep ourselves always healthy and strong in mind and intelligence so that we can distinguish the goal of life from a life full of problems. A thoughtful man must act in this way, learning to distinguish right from wrong, and thus attain the goal of life.