SB 7.2.49

atha nityam anityaṁ vā
 neha śocanti tad-vidaḥ
nānyathā śakyate kartuṁ
 sva-bhāvaḥ śocatām iti
Word for word: 
atha — therefore; nityam — the eternal spirit soul; anityam — the temporary material body; vā — or; na — not; iha — in this world; śocanti — they lament for; tat-vidaḥ — those who are advanced in knowledge of the body and soul; na — not; anyathā — otherwise; śakyate — is able; kartum — to do; sva-bhāvaḥ — the nature; śocatām — of those prone to lamentation; iti — thus.
Translation: 
Those who have full knowledge of self-realization, who know very well that the spirit soul is eternal whereas the body is perishable, are not overwhelmed by lamentation. But persons who lack knowledge of self-realization certainly lament. Therefore it is difficult to educate a person in illusion.
Purport: 

According to the mīmāṁsā philosophers, everything is eternal, nitya, and according to the Sāṅkhya philosophers everything is mithyā, or anitya — impermanent. Nonetheless, without real knowledge of ātmā, the soul, such philosophers must be bewildered and must continue to lament as śūdras. Śrīla Śukadeva Gosvāmī therefore said to Parīkṣit Mahārāja:

śrotavyādīni rājendra
 nṛṇāṁ santi sahasraśaḥ
apaśyatām ātma-tattvaṁ
 gṛheṣu gṛha-medhinām

“Those who are materially engrossed, being blind to knowledge of the ultimate truth, have many subjects for hearing in human society, O Emperor.” (Bhāg. 2.1.2) For ordinary persons engaged in material activities there are many, many subject matters to understand because such persons do not understand self-realization. One must therefore be educated in self-realization so that under any circumstances in life he will remain steady in his vows.