I suspect that the question arises from the false doctrine of ‘once saved, always saved’.
While we draw breath we are subject to being drawn away of our own desires.
James 1:14 But every man is tempted, when he is drawn away of his own lust, and enticed. 15 Then when lust hath conceived, it bringeth forth sin: and sin, when it is finished, bringeth forth death.
By belief of the gospel and baptism into Christ we have remission for all sin committed prior to baptism. After baptism we will still sin despite our best efforts and we can have forgiveness for sin by confession in prayer.
If we take Paul for an example:
1 Timothy 1:15 This is a faithful saying, and worthy of all acceptation, that Christ Jesus came into the world to save sinners; of whom I am chief.
Paul, converted on the road to Damascus, was baptised for the remission of his sins.
Acts 22:16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
He explains his daily struggle with sin.
Romans 7:18 For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. 19 For the good that I would I do not: but the evil which I would not, that I do. 20 Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me. 21 I find then a law, that, when I would do good, evil is present with me. 22 For I delight in the law of God after the inward man: 23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members. 24 O wretched man that I am! who shall deliver me from the body of this death? 25 I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.
For this reason he recognises that he is not already saved.
Philippians 3:11 If by any means I might attain unto the resurrection of the dead. 12 Not as though I had already attained, either were already perfect: but I follow after, if that I may apprehend that for which also I am apprehended of Christ Jesus. 13 Brethren, I count not myself to have apprehended: but this one thing I do, forgetting those things which are behind, and reaching forth unto those things which are before, 14 I press toward the mark for the prize of the high calling of God in Christ Jesus.
He knows that without due diligence it is possible to fall away.
1 Corinthians 9:24 Know ye not that they which run in a race run all, but one receiveth the prize? So run, that ye may obtain. 25 And every man that striveth for the mastery is temperate in all things. Now they do it to obtain a corruptible crown; but we an incorruptible. 26 I therefore so run, not as uncertainly; so fight I, not as one that beateth the air: 27 But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway.
He cites the example of Israel. They all heard the gospel, they were all baptised (in a figure) but many subsequently perished.
1 Corinthians 9:1 Moreover, brethren, I would not that ye should be ignorant, how that all our fathers were under the cloud, and all passed through the sea; 2 And were all baptized unto Moses in the cloud and in the sea; 3 And did all eat the same spiritual meat; 4 And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ. 5 But with many of them God was not well pleased: for they were overthrown in the wilderness.
Hebrews 4:2 For unto us was the gospel preached, as well as unto them: but the word preached did not profit them, not being mixed with faith in them that heard it.
Paul’s advice is that we must work out our own salvation with fear and trembling.
Philippians 2:12 Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling.
Some fall away
1 Timothy 1:18 This charge I commit unto thee, son Timothy, according to the prophecies which went before on thee, that thou by them mightest war a good warfare; 19 Holding faith, and a good conscience; which some having put away concerning faith have made shipwreck:
It was only at the end of his life that Paul was confident of salvation, but we have to remember that he had the Holy Spirit.
2 Timothy 4:6 For I am now ready to be offered, and the time of my departure is at hand. 7 I have fought a good fight, I have finished my course, I have kept the faith: 8 Henceforth there is laid up for me a crown of righteousness, which the Lord, the righteous judge, shall give me at that day:
John explains about the forgiveness of sins for those in Christ.
1 John 1:7 But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. 8 If we say that 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 that we have not sinned, we make him a liar, and his word is not in us.
1 John 2:1 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous: 2 And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.
From this we see (and find by experience) that in Christ we still sin, but our sins can be forgiven.
We notice that in the parable of the judgment, the emphasis is not on sin it is entirely on the works of faith.
Matthew 25:40 And the King shall answer and say unto them, Verily I say unto you, Inasmuch as ye have done it unto one of the least of these my brethren, ye have done it unto me.
Matthew 25:45 Then shall he answer them, saying, Verily I say unto you, Inasmuch as ye did it not to one of the least of these, ye did it not to me.
To be saved our sins must be forgiven, and righteousness imputed to us on the basis of faith.
Romans 4:22 And therefore it (faith) was imputed to him (Abraham) for righteousness. 23 Now it was not written for his sake alone, that it was imputed to him; 24 But for us also, to whom it shall be imputed, if we believe on him that raised up Jesus our Lord from the dead; 25 Who was delivered for our offences, and was raised again for our justification.
Justification by faith, by definition, means that we are not justified by living a sinless life.
Hebrews 8:12 For I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more.
Romans 4:8 Blessed is the man to whom the Lord will not impute sin.
1 John 2:12 I write unto you, little children, because your sins are forgiven you for his name’s sake.
I hope you have found this helpful.
May God bless you,