SB 11.21.14

snāna-dāna-tapo-’vasthā-
 vīrya-saṁskāra-karmabhiḥ
mat-smṛtyā cātmanaḥ śaucaṁ
 śuddhaḥ karmācared dvijaḥ
Synonyms: 
snāna — by bathing; dāna — charity; tapaḥ — austerity; avasthā — by virtue of one’s age; vīrya — potency; saṁskāra — execution of ritual purification; karmabhiḥ — and prescribed duties; mat-smṛtyā — by remembrance of Me; ca — also; ātmanaḥ — of the self; śaucam — cleanliness; śuddhaḥ — pure; karma — activity; ācaret — he should perform; dvijaḥ — a twice-born man.
Translation: 
The self can be cleansed by bathing, charity, austerity, age, personal strength, purificatory rituals, prescribed duties and, above all, by remembrance of Me. The brāhmaṇa and other twice-born men should be duly purified before performing their specific activities.
Purport: 

The word avasthā indicates that when boys and girls are young they are kept pure by youthful innocence and that as they grow up they are kept pure through proper education and engagement. By one’s individual potency one should avoid sinful activities and the association of those inclined toward sense gratification. The word karma here refers to prescribed duties, such as worshiping the spiritual master and the Deity, chanting the Gāyatrī mantra three times daily and accepting spiritual initiation. The prescribed duties of the varṇāśrama system automatically purify one from the covering of false ego by dovetailing one’s bodily designation in appropriate religious activities. There are specific duties for brāhmaṇas, kṣatriyas, vaiśyas, śūdras, brahmacārīs, gṛhasthas, vānaprasthas and sannyāsīs, as described previously in this canto by the Lord Himself. The most significant word here is mat-smṛtyā (“by remembrance of Me”). Ultimately, one cannot avoid the infection of illusion through any process except Kṛṣṇa consciousness. The three modes of nature perpetually interact, and one must sometimes fall into the mode of ignorance and sometimes rise to the mode of goodness, uselessly rotating within the kingdom of illusion. But by Kṛṣṇa consciousness, remembrance of the Personality of Godhead, one can actually uproot one’s tendency to act against the will of the Absolute Truth. Then one becomes freed from the clutches of māyā and goes back home, back to Godhead. As stated in the Garuḍa Purāṇa:

apavitraḥ pavitro vā
 sarvāvasthāṁ gato ’pi vā
yaḥ smaret puṇḍarīkākṣaṁ
 sa bāhyābhyantare śuciḥ

“Whether one is pure or contaminated, and regardless of one’s external situation, simply by remembering the lotus-eyed Personality of Godhead one can internally and externally cleanse one’s existence.”

Lord Caitanya recommended that we constantly remember the Supreme Lord by chanting His holy names, Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. This sublime process is essential for every human actually desirous of purifying his existence.