One who has forsaken his material occupations to engage in the devotional service of the Lord may sometimes fall down while in an immature stage, yet there is no danger of his being unsuccessful. On the other hand, a nondevotee, though fully engaged in occupational duties, does not gain anything.
As far as the duties of mankind are concerned, there are innumerable duties. Every man is duty-bound not only to his parents, family members, society, country, humanity, other living beings, the demigods, etc., but also to the great philosophers, poets, scientists, etc. It is enjoined in the scriptures that one can relinquish all such duties and surrender unto the service of the Lord. So if one does so and becomes successful in the discharge of his devotional service unto the Lord, it is well and good. But it so happens sometimes that one surrenders himself unto the service of the Lord by some temporary sentiment, and in the long run, due to so many other reasons, he falls down from the path of service by undesirable association. There are so many instances of this in the histories. Bharata Mahārāja was obliged to take his birth as a stag due to his intimate attachment to a stag. He thought of this stag when he died. As such, in the next birth he became a stag, although he did not forget the incident of his previous birth. Similarly, Citraketu also fell down due to his offenses at the feet of Śiva. But in spite of all this, the stress is given here to surrendering unto the lotus feet of the Lord, even if there is a chance of falling down, because even though one falls down from the prescribed duties of devotional service, he will never forget the lotus feet of the Lord. Once engaged in the devotional service of the Lord, one will continue the service in all circumstances. In the Bhagavad-gītā it is said that even a small quantity of devotional service can save one from the most dangerous position. There are many instances of such examples in history. Ajāmila is one of them. Ajāmila in his early life was a devotee, but in his youth he fell down. Still he was saved by the Lord at the end.
(Śrīmad-Bhāgavatam 1.15.17, Text and Bhaktivedanta Purport)