Even if a person is fully addicted to all sorts of sinful acts, if he happens to be engaged in the loving transcendental service of the Lord under proper guidance, he is to be considered the most perfect holy man without a doubt. And thus any person, whatsoever and whosoever he or she may be—even the fallen woman, the less intelligent laborer, the dull mercantile man, or even a man lower than all these—can attain the highest perfection of life by going back home, back to Godhead, provided he or she takes shelter of the lotus feet of the Lord in all earnestness. This sincere earnestness is the only qualification that can lead one to the highest perfectional stage of life, and unless and until such real earnestness is aroused, there is a difference between cleanliness or uncleanliness, learning or nonlearning, in the material estimation. Fire is always fire, and thus if someone touches thefire, knowingly or unknowingly, the fire will act in its own way without discrimination. The principle is: harir harati pāpāni duṣṭa-cittair api smṛtaḥ. The all-powerful Lord can purify the devotee of all sinful reactions, just as the sun can sterilize all sorts of infections by its powerful rays. "Attraction for material enjoyment cannot act upon a pure devotee of the Lord." There are hundreds and thousands of aphorisms in the revealed scriptures. Ātmārāmāś ca munayaḥ: "Even the self-realized souls are also attracted by the transcendental loving service of the Lord." Kecit kevalayā bhaktyā vāsudeva-parāyaṇāḥ: (S.B.6:1:15) "Simply by hearing and chanting, one becomes a great devotee of Lord Vāsudeva." Na calati bhagavat-padāravindāl lavanimiṣārdham api sa vaiṣṇavāgryaḥ: "A person who does not move from the lotus feet of the Lord even for a moment or a second is to be considered the greatest of all Vaiṣṇavas." Bhagavat-pārṣadatāṁ prāpte mat-sevayā pratītaṁ te: "The pure devotees are convinced of attaining the association of the Personality of Godhead, and thus they are always engaged in the transcendental loving service of the Lord." Therefore in all continents, in all planets, in all universes, devotional service to the Lord, or bhakti-yoga, is current, and that is the statement of the Śrīmad-Bhāgavatam and allied scriptures.
(Srimad Bhagavatam--2:9:36--purport).

Every endeavor is covered by some fault, just as fire is covered by smoke. Therefore one should not give up the work born of his nature, O son of Kuntī, even if such work is full of fault.
In conditioned life, all work is contaminated by the material modes of nature. Even if one is a brāhmaṇa, he has to perform sacrifices in which animal killing is necessary. Similarly, a kṣatriya, however pious he may be, has to fight enemies. He cannot avoid it. Similarly, a merchant, however pious he may be, must sometimes hide his profit to stay in business, or he may sometimes have to do business on the black market. These things are necessary; one cannot avoid them. Similarly, even though a man is a śūdra serving a bad master, he has to carry out the order of the master, even though it should not be done. Despite these flaws, one should continue to carry out his prescribed duties, for they are born out of his own nature.
A very nice example is given herein. Although fire is pure, still there is smoke. Yet smoke does not make the fire impure. Even though there is smoke in the fire, fire is still considered to be the purest of all elements. If one prefers to give up the work of a kṣatriya and take up the occupation of a brāhmaṇa, he is not assured that in the occupation of a brāhmaṇa there are no unpleasant duties. One may then conclude that in the material world no one can be completely free from the contamination of material nature. This example of fire and smoke is very appropriate in this connection. When in wintertime one takes a stone from the fire, sometimes smoke disturbs the eyes and other parts of the body, but still one must make use of the fire despite disturbing conditions. Similarly, one should not give up his natural occupation because there are some disturbing elements. Rather, one should be determined to serve the Supreme Lord by his occupational duty in Kṛṣṇa consciousness. That is the perfectional point. When a particular type of occupation is performed for the satisfaction of the Supreme Lord, all the defects in that particular occupation are purified. When the results of work are purified, when connected with devotional service, one becomes perfect in seeing the self within, and that is self-realization.
(Bhagavad-Gita-18:48--translation and purport).