Yes and no. It is all too common among evangelicals who rightly believe the Spirit works in us, for us to use our own internal sense of peace, or a lack thereof, as our own personal moral guide when faced with moral choices. The sole reason this might be appropriate, however, has nothing whatever to do with whatever moral dilemma we might be facing and everything to do with a clear biblical principle- whatever is not of faith is sin (Romans 14:23). The principle here is simple enough- if we do something we believe to be wrong, even if it is not in itself wrong, we have done wrong. My lack of peace is a clear sign I think something a sin. If I go ahead and do it, I have sinned, even if my lack of peace was misguided. Suppose, for instance, that it is not a sin to play the card game Hearts. Suppose, however, that you have been taught that such is a sin. I invite you to play the game. You wrestle over the invitation, have no peace about playing, and join in anyway, you have sinned. Note carefully that even here it would not be that playing Hearts is a sin, even for you. Rather the sin is acting against your conscience.
This does not work, however, in the opposite direction. That is, your feeling of peace is not at all a sure sign that what you have done is moral. Suppose I am tempted to commit adultery. I assess my own internal sense of peace. I feel fine about committing adultery. So I commit adultery. I will, because adultery is wrong, stand guilty before the living God for my sin. My sense of peace not only does not undo the sinfulness of the sin, it actually makes it worse. That is, not only would I, in this situation, be an adulterer, but would be a shameless one as well. My peace about my sin would not make my sin less a sin but would expose a calloused and recalcitrant heart.
Our calling, contra the faux gospel of pop culture, isn’t to follow our hearts. Our calling is to have our hearts informed by, directed by, the clear and plain teaching of the Word of God. We do not ultimately stand on our conscience, but on the Word of God. We ask, when confronted with a difficult ethical question, not “What says my heart?” but “What says the Word?” It, remember, equips us for every good work (II Timothy 3:16). When we look to our hearts I fear either we are looking to excuse our sin, or looking to excuse our laziness in studying God’s revealed will in His Word.
A lack of peace may mean you need to repent. A sense of peace, however, doesn’t mean you don’t need to repent. Let’s stop trusting ourselves, our own wisdom, our own discernment, and be Berean about our own deceitful hearts. Trust in the Lord with all your heart, And lean not on your own understanding; In all your ways acknowledge Him, And He shall direct your paths (Proverbs 3:5).