My dear, , sometimes on the path of Krishna consciousness a devotee may experience a fall down in regards to following the four regulative principles. This does not mean that he should become discouraged and give up his endeavor to awaken his dormant Krishna consciousness. Rather he should learn from his fall down, pick himself, and continue with his endeavor to awaken his dormant Krishna consciousness. If he does so his ultimate success is guaranteed.

To encourage the fallen devotee Srila Prabhupada has written in Chapter 6 of his book The Path of Perfection as follows;

In this regard, there is the story of Viśvāmitra Muni, a great king, a kṣatriya, who renounced his kingdom and took to the yoga process in order to become more spiritually advanced. At that time the meditational yoga process was possible to execute. Viśvāmitra Muni meditated so intently that Indra, the King of heaven, noticed him and thought, ' 'This man is trying to occupy my post." The heavenly planets are also material, and there is competition—no businessman wants another businessman to exceed him. fearing that Viśvāmitra Muni would actually depose him, Indra sent one heavenly society girl, named Menakā, to allure him sexually. Menakā was naturally very beautiful, and she was intent on disrupting the muni's meditations. Indeed, he became aware of her feminine presence upon hearing the sound of her bangles, and he immediately looked up from his meditation, saw her, and became captivated by her beauty. As a result, the beautiful girl Śakuntalā was born by their conjugation. When Śakuntalā was born, Viśvāmitra lamented: "Oh, I was just trying to cultivate spiritual knowledge, and again I have been entrapped." He was about to flee when Menakā brought his beautiful daughter before him and chastised him. Despite her pleading, Viśvāmitra resolved to leave anyway.
 

Thus there is every chance of failure on the yogic path; even a great sage like Viśvāmitra Muni can fall down due to material allurement. Although the muni fell for the time being, he again resolved to go on with the yoga process, and this should be our resolve. Kṛṣṇa informs us that such failures should not be cause for despair. There is the famous proverb that "failure is the pillar of success." In the spiritual life especially, failure is not discouraging. Kṛṣṇa very clearly states that even if there is failure, there is no loss either in this world or in the next. One who takes to this auspicious line of spiritual culture is never completely vanquished.

So even if one has a fall down he should not give up Krishna consciousness.  He should take advantage of his fall down to become more solidly situated on the pathway back to home, back to Godhead.