There is a difference between being deceived in our mind and in our heart. Feelings accompany a deceived heart, while confusion and instability are more likely to accompany a deceived mind. The mind can be changed by hearing and believing the truth– the heart, not so easily, because the feelings of the heart override truth and reason. So the most important thing is to keep your heart from being deceived, and that happens through feelings. If God is truly Lord of our heart, He will be Lord of our feelings, and they will be governed by love. "Keep thy heart with all diligence; for out of it are the issues of life." Proverbs 4:23