Scripture could not be more clear that we are sealed with the Holy Spirit to guarantee and ensure our salvation.
God is faithful even when we are faithless, (2 Timothy 2) because He knows our frame and remembers that we are dust. (Psalm 103)
Our Lord differs with you:
“Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but only the one who does the will of my Father in heaven."Saint Paul also had something to say on the matter:
(Matt 7:21)
Do you not know that the unjust will not inherit the kingdom of God? Do not be deceived; neither fornicators nor idolaters nor adulterers nor boy prostitutes nor sodomites nor thieves nor the greedy nor drunkards nor slanderers nor robbers will inherit the kingdom of God.Our Lord provided for the forgiveness of post-baptismal sins:
(1 Cor 6:9-10)
[Jesus] said to them again, “Peace be with you. As the Father has sent me, so I send you.” And when he had said this, he breathed on them and said to them, “Receive the holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained.”God said it, I believe it, that settles it.
(John 20:21-23)
"Most assuredly, I say to you, he who hears My word and believes in Him who sent Me has everlasting life, and shall not come into judgment, but has passed from death into life." (John 5:24)
Hebrews 10:10 By the which will we are sanctified through the offering of the body of Jesus Christ once for all. 11 And every priest standeth daily ministering and offering oftentimes the same sacrifices, which can never take away sins: 12 But this man, after he had offered one sacrifice for sins for ever, sat down on the right hand of God; 13 From henceforth expecting till his enemies be made his footstool. 14 For by one offering he hath perfected for ever them that are sanctified. 1 Corinthians 6:11 And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.
Hebrews 10:14 For by one offering he hath perfected for ever them that are sanctified.
The means by which we are saved is an unwavering faith in Jesus.
John 6:38-40 Jesus said, “I have come down from heaven not to do my will but to do the will of him who sent me. And this is the will of him who sent me, that I shall lose none of all that he has given me, but raise them up at the last day. For my Father’s will is that everyone who looks to the Son and believes in him shall have eternal life, and I will raise him up at the last day”
Rom. 3:28-30, "For we maintain that a man is justified by faith apart from works of the Law. 29 Or is God the God of Jews only? Is He not the God of Gentiles also? Yes, of Gentiles also, 30 since indeed God who will justify the circumcised by faith and the uncircumcised through faith is one."
Rom. 4:5, "But to the one who does not work, but believes in Him who justifies the ungodly, his faith is reckoned as righteousness,"
Rom. 5:1, "therefore having been justified by faith, we have peace with God through our Lord Jesus Christ,"
Romans 9:30 What shall we say then? That the Gentiles, which followed not after righteousness, have attained to righteousness, even the righteousness which is of faith. 31 But Israel, which followed after the law of righteousness, hath not attained to the law of righteousness. 32 Wherefore? Because they sought it not by faith, but as it were by the works of the law. For they stumbled at that stumblingstone;
Rom. 11:6, "But if it is by grace, it is no longer on the basis of works, otherwise grace is no longer grace."
Paul rebukes Peter for applying rules for salvation.
Gal. 2:16, "nevertheless knowing that a man is not justified by the works of the Law but through faith in Christ Jesus, even we have believed in Christ Jesus, that we may be justified by faith in Christ, and not by the works of the Law; since by the works of the Law shall no flesh be justified."
Gal. 2:21, I do not nullify the grace of God; for if righteousness comes through the Law, then Christ died needlessly.
Phil. 3:9, "and may be found in Him, not having a righteousness of my own derived from the Law, but that which is through faith in Christ, the righteousness which comes from God on the basis of faith."
Acts 13:39 and through Him everyone who believes is freed from all things, from which you could not be freed through the Law of Moses.
1 JOHN 2:12 I write to you, little children, because your sins are forgiven you for His name's sake.
Hebrew 10:14 For by one offering he hath perfected for ever them that are sanctified.
Relying on some legal earthly act is law not grace and faith.
And how do we know?
Romans 8:16 The Spirit itself beareth witness with our spirit, that we are the children of God:
You are correct. As Scripture says in 2 Peter 1:9
Matthew 7:15-27 15 “Beware of false prophets, who come to you in sheep's clothing but inwardly are ravenous wolves. 16 You will recognize them by their fruits. Are grapes gathered from thornbushes, or figs from thistles? 17 So, every healthy tree bears good fruit, but the diseased tree bears bad fruit. 18 A healthy tree cannot bear bad fruit, nor can a diseased tree bear good fruit. 19 Every tree that does not bear good fruit is cut down and thrown into the fire. 20 Thus you will recognize them by their fruits.
21 “Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven. 22 On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’ 23 And then will I declare to them, ‘I never knew you; depart from me, you workers of lawlessness.’
24 “Everyone then who hears these words of mine and does them will be like a wise man who built his house on the rock. 25 And the rain fell, and the floods came, and the winds blew and beat on that house, but it did not fall, because it had been founded on the rock. 26 And everyone who hears these words of mine and does not do them will be like a foolish man who built his house on the sand. 27 And the rain fell, and the floods came, and the winds blew and beat against that house, and it fell, and great was the fall of it.”
Those Christ says He never knew DID appeal to their works. Obviously their works didn't save them.
So that verse can't be used to support your claim.
1 Corinthians 6:9-11 9 Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, 10 nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God. 11 And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.
There were that no longer. They got saved out of that lifestyle and were saved. That doesn't mean that a believer who happens to fall into sin isn't saved any more. It's referring to unbelievers who are living in those sins. So that verse doesn't apply to support your contention either.
John 20:21-23 [Jesus] said to them again, “Peace be with you. As the Father has sent me, so I send you.” And when he had said this, he breathed on them and said to them, “Receive the holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained.”
1 John 1:7-10 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.
Believers sin and provision is made for forgiveness. There is no provision for retaining sin and it doesn't affect one's salvation. If it did, it would reduce salvation to being based on works. If you're good enough, you get in. If not, too bad for you.
If you don't get saved by works, you don't stay saved by works.
Galatians 3:1-10 O foolish Galatians! Who has bewitched you? It was before your eyes that Jesus Christ was publicly portrayed as crucified. 2 Let me ask you only this: Did you receive the Spirit by works of the law or by hearing with faith? 3 Are you so foolish? Having begun by the Spirit, are you now being perfected by the flesh? 4 Did you suffer so many things in vain—if indeed it was in vain? 5 Does he who supplies the Spirit to you and works miracles among you do so by works of the law, or by hearing with faith— 6 just as Abraham “believed God, and it was counted to him as righteousness”? 7 Know then that it is those of faith who are the sons of Abraham. 8 And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, “In you shall all the nations be blessed.” 9 So then, those who are of faith are blessed along with Abraham, the man of faith. O foolish Galatians! Who has bewitched you? It was before your eyes that Jesus Christ was publicly portrayed as crucified. 2 Let me ask you only this: Did you receive the Spirit by works of the law or by hearing with faith? 3 Are you so foolish? Having begun by the Spirit, are you now being perfected by the flesh? 4 Did you suffer so many things in vain—if indeed it was in vain? 5 Does he who supplies the Spirit to you and works miracles among you do so by works of the law, or by hearing with faith— 6 just as Abraham “believed God, and it was counted to him as righteousness”?
7 Know then that it is those of faith who are the sons of Abraham. 8 And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, “In you shall all the nations be blessed.” 9 So then, those who are of faith are blessed along with Abraham, the man of faith.
10 For all who rely on works of the law are under a curse; for it is written, “Cursed be everyone who does not abide by all things written in the Book of the Law, and do them.”