How do I know if I’ve truly repented?

Answer:

"Therefore, King Agrippa, I was not disobedient to the heavenly vision, but declared first to those in Damascus and in Jerusalem, and throughout all the region of Judea, and then to the Gentiles, that they should repent, turn to God, and do works befitting repentance" (Acts 26:19-20).

The word "repent" in this passage comes from the Greek word metanoeo. It is a compound word of meta (change) and noeo (to use the mind). It originally was used for hindsight, to reflect back on what you did, and to change your mind about it. In particular, it meant to reconsider something you did now regretting what you had done.

The word "turn" in this passage comes from the Greek word epistrepho. It too is a compound of epi (on) and strepho (turn). It means to turn around, do an about-face, and to be converted. The emphasis here is the change in behavior, to return to where you once were. Such as in Acts 15:36, where the same word is used to say "Let us go again." The idea of conversion is that you were once righteous and with God, but you left and are now returning (Romans 7:9-11). In other words, we don’t start life sinful; we started out righteous, but we then lost our way (Ecclesiastes 7:29). God calls us back, to be converted (Acts 3:19). We need to return to our shepherd (I Peter 2:25).

Why two descriptions? Because sin starts in our thoughts and then comes out in our actions (Mark 7:21-23). Therefore, to change, we must start with a change in our mind so that the change comes out in our actions. In other words, repentance is saying “No” to sin. Conversion is saying “Yes” to righteousness.

Repentance does not mean you will never sin in this way again. Satan knows you have a weakness for fornication so he is going to repeatedly attack that weak point. To say you will never sin again is to tell yourself a lie. "If we say that we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness" (I John 1:8-9).

John later states that the difference between a child of God and a child of Satan is in their response to sin. A child of God lives a life aimed at always doing what is right. On occasion, he will slip up, but he will shortly return to his normal path of striving for righteousness. In contrast, the child of Satan basically does what is wrong either out of lack of knowledge or a lack of caring. It doesn't mean such a person is totally bad. On occasion, even the worse person does what is right, but it doesn't last. He goes right back to sinning because that is his habit.

"No one who is born of God practices sin, because His seed abides in him; and he cannot sin, because he is born of God. By this the children of God and the children of the devil are obvious: anyone who does not practice righteousness is not of God, nor the one who does not love his brother" (I John 3:9-10).

Don't make the mistake of reading this as saying that a child of God never sins -- otherwise, you have John contradicting what he just said in John 1:8. It is clearer in the Greek. A child of God doesn't make a practice (or habit) of sin and he cannot remain in sin because he wants to follow God. A child of Satan does make a practice (or habit) of sin.

So how do you know if you have repented? You know it by your change in attitude toward your sexual sins. You know they are wrong and you don't make any excuses for your bad behavior. You don't try to explain it away by claiming that you could help yourself or that you had to do it. You freely admit that it was wrong. And you see that change in attitude in your change in behavior. You don't shed your clothes at an opportunity to have sex. You fight to remain pure, even if that means running away from the temptation. Habits are hard to break, but you are putting in every effort to break your bad habits. And if Satan ever does trap in sin, you don't give up and wallow in misery. You get right back up, figure out where you went wrong, and make further changes in your life so that a repeat is less likely.

You know you've repented because you are willing to fight to be righteous.