Matthew 15:19 For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies:
So when someone has evil thoughts where do they come from? Is sex sin a body problem or a heart problem? When people tell lies does that reveal anything about their heart? When people make light of the things of God what does that tell you about them in their heart and most central part to their lives.
The truth is what we say and do comes from who we are. If we could have a good heart we would change. If our heart was right then our sex life would please God. What we say and think would be right if our heart was right.
The obvious decision here is to work on our heart. That is to work on our inner most being. We do that first by His saving us. Then we do that by filling our heart with His Word, His way of thinking, His heart! So work on being transformed by the renewing of your mind.