Wrong behaviour needs to be avoided.
Gal 5:19-21 Now the works of the flesh are evident: sexual immorality, impurity, sensuality, (20) idolatry, sorcery, enmity, strife, jealousy, fits of anger, rivalries, dissensions, divisions, (21) envy, drunkenness, orgies, and things like these. I warn you, as I warned you before, that those who do such things will not inherit the kingdom of God.
Since we are saved by grace, not works, then it is sometimes suggested that we may continue doing wrong things. This is not correct.
Rom 6:1-2 What shall we say then? Are we to continue in sin that grace may abound? (2) By no means! How can we who died to sin still live in it?
A convert to Christ will make changes in his or her life. He or she will make right any relationship. To presume on God’s forgiveness suggests a lack of true repentance. It is not for us to say which specific sins of other people God will or will not forgive, other than to warn against presumptuous sins.
Heb 10:26-27 For if we go on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, (27) but a fearful expectation of judgment, and a fury of fire that will consume the adversaries.
We are all hesitant to condemn others because of Jesus warning:
John 8:6b-7 Jesus bent down and wrote with his finger on the ground. (7) And as they continued to ask him, he stood up and said to them, “Let him who is without sin among you be the first to throw a stone at her.”
It is our universal experience that wrong attitudes and behaviour are never very far away. This should keep us humble. But it is not a go-ahead to enter into sin wilfully.
Nevertheless we do all slip up. Sinful thought and sinful behaviour is not magically banished.
1Jn 1:6-10 If we say we have fellowship with him while we walk in darkness, we lie and do not practice the truth. (7) But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus his Son cleanses us from all sin. (8) If we say we have no sin, we deceive ourselves, and the truth is not in us. (9) If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. (10) If we say we have not sinned, we make him a liar, and his word is not in us.
It is just as well that we can be forgiven sins, else none of us would have any hope. So what is the difference between sins that will be forgiven and those that will stop us from inheriting the kingdom? I find that marriage helps me to appreciate such a difference. Husbands and wives will always make mistakes. Where there is love in the marriage or when love can be revived, there is hope. If we love God and genuinely desire to please him, then there is hope. There is sin that will not and cannot be forgiven (Heb 10:26 quoted above). That is sin that that cannot be repented of because the sinner does not love God any longer.
How then do we deal with our desires, especially sexual ones? If we focus on ourselves and not on God and on other people then it will be impossible.
Rom 8:6 For to set the mind on the flesh is death, but to set the mind on the Spirit is life and peace.
Php 4:8 Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things.
Human pride can be at the heart of lustful thoughts; pride fans wrong desires as air fans a fire. If we allow God to develop in us humility, then this can guard our thoughts.
As I understand the Bible about the subject, satisfying sexual desires is not wrong as such, for married or single person. (E.g. masturbation is not a sin as such, but becomes a sin when a person imagines in sexual context someone who is not their spouse.)
The question “How do you deal with sexual desire?” is too general. General advice might be physical exercises, distractions, concentrate on serving God in many different ways.
When we repent sincerely, God always forgives us. If we are addicted to some ways of satisfying sexual desires, we need to ask for help, e.g. from people who have been through and coped with similar difficulties. Sometimes professional counselling is needed, because addictions can be extremely hard to cope with, if we struggle with them without help of trusted people.