What does it mean to be a fornicator? Does it mean, "I committed it today, but I won't tomorrow," but doing it the next day anyway?
If repentance is changing habits, then such a person remains as a fornicator and is a fallen brother or sister. That person can't keep on being called a Christian. Or can they?
Even if the person feels guilty, if that person doesn't change, then it's the sadness according to the world and not according to God. Eventually, it'll produce death because that's what the sadness according to the world does. By the term "death", I think it means getting numb to sin and not wanting to go back to God.
Am I wrong about it all?
Also, there's the passage where Paul said: If they cannot control themselves, let them marry. I don't think it means that these people are already having sex. I think there's the risk of falling into sin. Or are they already doing it?
When God looks at a person, He sees who the person is -- not who he used to be or what he claims he will be in the future -- but who he actually at this moment in time.
"The soul who sins shall die. The son shall not bear the guilt of the father, nor the father bear the guilt of the son. The righteousness of the righteous shall be upon himself, and the wickedness of the wicked shall be upon himself.
But if a wicked man turns from all his sins which he has committed, keeps all My statutes, and does what is lawful and right, he shall surely live; he shall not die. None of the transgressions which he has committed shall be remembered against him; because of the righteousness which he has done, he shall live. "Do I have any pleasure at all that the wicked should die?" says the Lord GOD, "and not that he should turn from his ways and live?"
But when a righteous man turns away from his righteousness and commits iniquity, and does according to all the abominations that the wicked man does, shall he live? All the righteousness which he has done shall not be remembered; because of the unfaithfulness of which he is guilty and the sin which he has committed, because of them he shall die" (Ezekiel 18:20-24).
A person commits fornication when he has sex with someone to whom he is not married. So long as that sin is not dealt with through repentance, he is a fornicator. When he turns from his sins and is obedient to God, being baptized if he was not already a Christian (Acts 22:16) or praying to God for forgiveness if he a Christian (I John 1:8-2:1), then he is released from the debt of his sin. The question is the sincerity of his repentance, and that is something you or I cannot judge. If a person says he has repented, we must assume that such is the case. "And if he sins against you seven times in a day, and seven times in a day returns to you, saying, 'I repent,' you shall forgive him" (Luke 17:4).
Assuming that a man sincerely repented of fornication, but through weakness repeated his error, this does not necessarily mean that his original repentance was not sincere. If he truly wants out of his sin, then he will be asking for forgiveness again and searching for ways to no repeat the sin.
An insincere repentance would be a man who claims to repent of his fornication, but then makes no changes in his life. Perhaps he is living with a woman. He says he repents of fornication, but doesn't move out of the house. It is his lack of action toward improving his morality and not his repeated sexual acts that proves his had not repented.
As a different example, I had a boy once tell me that he was going to try and get off of drugs. He would not stay where he could be monitored, he said he would be staying with people who were known drug users, yet he expected me to accept that he was going to sincerely try to stop using drugs. I didn't accept his words because his actions said he was lying.
Getting numb to sin is actually what the word "licentiousness" or "lewdness" is about. A person gets so used to sin that he comes to believe he has a right or a license to sin. When a person doesn't care what other people think, when he is going to sin because that is what he wants to do, then he ends up spiritually dead because he won't listen to the words that can restore him to life.
"But I say to the unmarried and to the widows: It is good for them if they remain even as I am; but if they cannot exercise self-control, let them marry. For it is better to marry than to burn with passion" (I Corinthians 7:8-9).
Paul's wording is broader than not restraining ones self from fornication. The Greek actually says "than to burn." The translators add "with passion" because that is the type of burning implied, though not stated. People who want to stop committing fornication but who do not believe they can control their sexual impulses should get married. But such is also true of a people who are not exercising restraint in acts of passion which might lead to fornication.
Ideally, Christians ought to have control over their sexual desires, but if they find themselves weak and they are sincere in their desire to please God, then the obvious solution is to get married. Then they are able to express themselves sexually without sinning.