For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false testimony, slander.
"You have heard that it was said to those of old, 'You shall not commit adultery.' 28 But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart.
1 Cor 10:8
Nor let us commit sexual immorality, as some of them did, and in one day twenty-three thousand fell;
1 Thess 4:3-5
It is God's will that you should be sanctified: that you should avoid sexual immorality; that each of you should learn to control his own body in a way that is holy and honorable, 5 not in passionate lust like the heathen, who do not know God;
Sexual Immorality is probably the biggest issue that plagues anyone desiring to walk a Christian walk. And when I talk about sexual immorality, I am talking about adultery, lusting after somebody, pornography... anything that causes you to desire something in an ungodly way. It's not an issue that too many people are willing to confess to. But it's one that if you don't bring it to the light, it will follow you and tempt you day in and day out.
Confess your trespasses to one another, and pray for one another, that you may be healed. The effective, fervent prayer of a righteous man avails much.
1 John 1:9
If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.
To me, sexual sin and/or it's desires, is the equivalent as drug or alcohol
addiction. Its not something that just goes away. I have known people that said
that when they prayed over sexual addiction God just took the desire away from
them. Most people I know that talk about this, they still deal with it. And that
does not make any one a bad Christian. It means we have an issue that we have to
confront and overcome.
Just as Paul had a thorn in his flesh that he had to contend with we need to rely on God's grace. That does not mean we can follow through with adultery, porn or any type of sexual sin and think we are walking in line with God's plan for us. And when were not walking according to his plan you might wonder why prayers may not be getting answered.
1 Cor 10:13
No temptation has overtaken you except such as is common to man; but God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will also make the way of escape, that you may be able to bear it.
So how do we deal with it then? One day at a time. I know I love God enough that I will do what I have to to keep myself from falling to sin. And when I feel that temptation is starting to overcome me anyway, then the fear of God is remembering that I will be judged according to what I do while here on earth. So consider another scripture.
"You have heard that it was said to those of old, 'You shall not commit adultery.' 28 But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart. 29 If your right eye causes you to sin, pluck it out and cast it from you; for it is more profitable for you that one of your members perish, than for your whole body to be cast into hell. 30 And if your right hand causes you to sin, cut it off and cast it from you; for it is more profitable for you that one of your members perish, than for your whole body to be cast into hell.
See also Masturbation