There is a problem with sins that do not feel very wrong (or wrong at all). This problem is that a Christian, in that situation, sort of has to force themselves to repent and to act like something is wrong, but they themselves do not actually feel it is really hurting anyone and so they cannot really make themselves feel, rather than think, it is wrong.
I believe this could be an influence that motivates Christians to give up their faith, because people get tired of saying things are evil or sinful when they don't actually feel those acts hurt anyone.
Here are some interesting verses written in Psalm 119 about this issue:
18 Open my eyes, that I may behold wondrous things out of your law.
27 Make me understand the way of your precepts, and I will meditate on your wondrous works.
33 Teach me, O LORD, the way of your statutes; and I will keep it to the end.
34 Give me understanding, and I will keep your law and obey it with all my heart.
73 Your hands have made and fashioned me; give me understanding that I may learn your commandments.
125 I am your servant; give me discernment that I may understand your statutes.
The psalmist prays specifically for understanding of God's laws, to see why they are right or how they make sense. So the psalmist is praying not to follow God's law out of an iron sense of obligation, but to follow it because they can say, 'I can actually agree with that command, I can see how that makes sense and is the right thing to do'. Then they can feel the rightness or wrongness of a command because it makes sense.
So it seems that it's important to be able to rationally see how something is a sin if you say it is a sin, and for many people that means tracing it to some kind of harm - self-harm, harm of others, or harm of God.
So one conclusion is that some things we consider sins may actually not be sins, and we are being too hard on ourselves, because we cannot trace it back to a rational basis. A verse that relates to this is from 1 Corinthians 4:6, where people in the church had been adding to what the Bible said:
"Now, brothers and sisters, I have applied these things to myself and Apollos for your benefit, so that you may learn from us the meaning of the saying, “Do not go beyond what is written.” Then you will not be puffed up in being a follower of one of us over against the other."
Another conclusion is that we can trace it to a rational basis after thinking about it a lot, and this will help us do it joyously rather than from inexplicable guilt, e.g. "I can see now how that action might be harmful in some way and why I shouldn't do it".