Here are some things I've found helpful...
To the pure all things are pure, but to those who are defiled and unbelieving nothing is pure; but even their mind and conscience are defiled. -Titus 1:15
If I go to a chinese restaurant which happens to be sporting the typical overweight buddha statue in the lobby, I could potentially imagine that I'm partaking in some pagan worship practice by eating at the restaurant. As a christian, I know that that would not be good, so I might also imagine that God would be angry with me for departing from Him in a sense by "eating in an idol's temple," so to speak, but still believing that the idol has some sort of power over me as if it were something magical or demonic. On the other hand, I can choose to believe that "the earth is the Lord's and all of its fulness," that idols are nothing but material substance, and that Chinese food is just tasty food that I could be thankful for. In the latter case, by choosing to believe scripture, my conscience is cleansed and I struggle with less temptation which could potentially stumble me.
That brings me to see moral good and evil as having no physical substance, and while that in itself is a huge relief, it opens the door to seeing righteousness and unrighteousness as a matter pertaining to the inner self, in which case, the following is relevant:
Search me, O God, and know my heart;
Try me, and know my anxieties;
And see if there is any wicked way in me,
And lead me in the way everlasting. -Ps 139:23,24
There is therefore now no condemnation to those who are in Christ Jesus, who do not walk according to the flesh, but according to the Spirit. For the law of the Spirit of life in Christ Jesus has made me free from the law of sin and death. -Rom 8:1,2
Do not be deceived, God is not mocked; for whatever a man sows, that he will also reap. -Gal 6:7
In my own life it has been a slow process of learning what is and is not acceptable to God as it pertains to desires, drives and motives, that faith really does "cleanse" the "heart" or inward man, and that doubting leads into sin.