SB 11.20.22

sāṅkhyena sarva-bhāvānāṁ
 pratilomānulomataḥ
bhavāpyayāv anudhyāyen
 mano yāvat prasīdati
Synonyms: 
sāṅkhyena — by analytic study; sarva — of all; bhāvānām — material elements (cosmic, earthly and atomic); pratiloma — by regressive function; anulomataḥ — by progressive function; bhava — creation; apyayau — annihilation; anudhyāyet — should constantly observe; manaḥ — the mind; yāvat — until; prasīdati — is spiritually satisfied.
Translation: 
Until one’s mind is fixed in spiritual satisfaction, one should analytically study the temporary nature of all material objects, whether cosmic, earthly or atomic. One should constantly observe the process of creation through the natural progressive function and the process of annihilation through the regressive function.
Purport: 

There is a saying that whatever goes up must come down. Similarly, Lord Kṛṣṇa states in the Bhagavad-gītā (2.27):

jātasya hi dhruvo mṛtyur
 dhruvaṁ janma mṛtasya ca
tasmād aparihārye ’rthe
 na tvaṁ śocitum arhasi

“For one who has taken his birth, death is certain; and for one who is dead, birth is certain. Therefore, in the unavoidable discharge of your duty, you should not lament.” Mano yāvat prasīdati: Until one has established one’s consciousness on the liberated platform of perfect knowledge, one must constantly ward off the attacks of illusion through rigid analytic observation of material nature. The material mind may be attracted to sex; therefore by spiritual intelligence one should scrutinize the temporary nature of one’s own body and the body that has artificially become the object of one’s material lust. One may apply this rigid analysis to all material bodies, from the fantastic cosmic body of Lord Brahmā down to that of the most insignificant germ. As previously stated by Lord Kṛṣṇa, one who is advanced in Kṛṣṇa consciousness spontaneously avoids sense gratification and is constantly drawn by spiritual love into his relationship with Lord Kṛṣṇa. One who has not achieved the platform of spontaneous Kṛṣṇa consciousness must remain constantly vigilant so as not to be grossly cheated by the material energy of the Lord. One who tries to exploit the material energy ruins his spiritual life and experiences varieties of misery.