In order to actually hear Paramatma's voice from within for guidence one needs the required purification. This given in Srimad Bhagavad Gita 3.17
yas tv ātma-ratir eva syād
ātma-tṛptaś ca mānavaḥ
ātmany eva ca santuṣṭas
tasya kāryaḿ na vidyate
But for one who takes pleasure in the self, whose human life is one of self-realization, and who is satisfied in the self only, fully satiated — for him there is no duty.
A person who is fully Kṛṣṇa conscious, and is fully satisfied by his acts in Kṛṣṇa consciousness, no longer has any duty to perform. Due to his being Kṛṣṇa conscious, all impiety within is instantly cleansed, an effect of many, many thousands of yajñaperformances. By such clearing of consciousness, one becomes fully confident of his eternal position in relationship with the Supreme. His duty thus becomes self-illuminated by the grace of the Lord, and therefore he no longer has any obligations to the Vedic injunctions. Such a Kṛṣṇa conscious person is no longer interested in material activities and no longer takes pleasure in material arrangements like wine, women and similar infatuations.
Till then one has to go by Vipra, dharma and achyuta (brahmana, dharma and Krishna).
The so-called Conscience is only conditioning or one's habit. Someone maybe be conditioned not to spoeak lies. So when a situation arise to speak a lie his so-called conscience prevents him to do so. But in due course of time this conditioning can wane away or change. Hence we should follow vipra, dharma and achyuta.