About 5 minutes to read
I keep going back to the same sin
If you think a real Christian would be free of this by now, read Romans 7. Paul wrote it as an apostle, and he says he does the very thing he hates. There is a war in every believer between the flesh and the spirit, and it lasts as long as this life (WCF 13.2).
God doth continue to forgive the sins of those that are justified; and although they can never fall from the state of justification, yet they may by their sins fall under God’s fatherly displeasure, and not have the light of his countenance restored unto them, until they humble themselves, confess their sins, beg pardon, and renew their faith and repentance.
Westminster Confession of Faith 11.5
God gave his verdict when you believed, and he does not reopen the case. What your sin can bring on you is his fatherly displeasure. He may hide the light of his face until you come back humbled and confess it, and he may use the rod, yet he will not take his lovingkindness from you (Psalm 89:30-33). That is a father correcting his son, and there is nothing of the judge in it.
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: And he is the propitiation for our sins:
1 John 2:1-2 (KJV)
Your advocate does not plead that you are innocent. He pleads his own blood, and that plea does not wear thin as your record grows, because it never rested on your record.
So do not hide the sin, and do not make peace with it. Name it to God each time you fall, and let a brother you trust know what you are fighting. Romans 13:14 says not to make provision for the flesh, so if you keep falling in the same place at the same hour, change the place and the hour. Remaining sin may prevail for a time, but the part of you that is born again will overcome, because the Spirit of Christ keeps giving it strength (WCF 13.3). For the long fight itself, read A Greater Affection.
What I did is too great to forgive
You may carry one sin heavier than all the rest. If you did it after you came to Christ, it may feel heavier still.
As there is no sin so small but it deserves damnation, so there is no sin so great that it can bring damnation upon those who truly repent.
Westminster Confession of Faith 15.4
David took another man’s wife and had the man killed to cover it. When he confessed, Nathan told him the Lord had put away his sin (2 Samuel 12:13). The consequences stayed in his house, but the guilt was gone. Paul had hunted Christians into prison. He called himself the chief of sinners and said Christ showed him mercy as a pattern for everyone who would believe after him (1 Timothy 1:15-16). If your sin is great, that pattern was set up for sinners like you.
Once you have confessed it and turned from it, trusting Christ’s blood and not your confession, the pardon is yours. The memory may come back for years, and the shame with it, but the guilt does not. Take him at his word, and thank him for it.
He must be tired of forgiving me
We tire of forgiving because every pardon costs us something. Your pardon cost God his Son, and that price was paid once and in full. He is not paying it again each time you come.
Who is a God like unto thee, that pardoneth iniquity, and passeth by the transgression of the remnant of his heritage? he retaineth not his anger for ever, because he delighteth in mercy. He will turn again, he will have compassion upon us; he will subdue our iniquities; and thou wilt cast all their sins into the depths of the sea.
Micah 7:18-19 (KJV)
He has promised to subdue the very sins he pardons. And when Peter asked how often he must forgive his brother, Jesus said seventy times seven (Matthew 18:22). He does not ask more mercy of you than he shows you.
While you wait
Do Not Fight This Alone
A page cannot sit with you or pray over you. Tell your pastor or an elder what you are afraid of. Keep sitting under the preached Word, and if you are a communing member, do not stay away from the Lord’s Table while your doubts are being answered. The Larger Catechism says it was appointed for the relief even of weak and doubting Christians (Q&A 172). Safe in His Keeping gives a few things to do while you wait for the fear to lift.
If you cannot tell whether you have ever come to Christ, do not wait to settle it. Come to him now. He promised to cast out none who come (John 6:37), and the gospel is set out for you in full.