I thank Christ Jesus our Lord, who has given me strength, that he considered me trustworthy, appointing me to his service. Even though I was once a blasphemer and a persecutor and a violent man, I was shown mercy because I acted in ignorance and unbelief. The grace of our Lord was poured out on me abundantly, along with the faith and love that are in Christ Jesus. Here is a trustworthy saying that deserves full acceptance: Christ Jesus came into the world to save sinners—of whom I am the worst. But for that very reason I was shown mercy so that in me, the worst of sinners, Christ Jesus might display his immense patience as an example for those who would believe in him and receive eternal life. Now to the King eternal, immortal, invisible, the only God, be honor and glory for ever and ever. Amen. (1 Timothy 1:12-17 NIV)
To struggle about “that one sin” is the work of Satan and the spiritual forces of evil. They have too many willing human agents to assist them in creating hardships in people. For example, some people struggle all their days because they were sexually abused as a child. Many times the victim of abuse feels guilty for the abuse, and so they can come to struggle with “that one sin”. Others are responsible for their own struggles. Satan’s foremost goal is to oppose the work of God and to destroy God’s people. He hates us and is most happy when we are miserable, despairing, and desperate about our condition. We must always remember the malicious intent of the enemy. Be alert and of sober mind. Your enemy the devil prowls around like a roaring lion looking for someone to devour (1 Peter 5:8 NIV). Read that again. Devour. He seeks our destruction; he wants to rid the earth of us, or at least to make us totally ineffective for God.
The best advertising for the gospel is joyful, loving believers. Satan despises those who rejoice that their sins are forgiven and who want to express love for God and others. If he can get the follower of Christ to fixate on doubt of forgiveness and justification, he can hinder that person from rejoicing and acting in love. For he or she will become too focused on his or her own self. Satan can point at miserable Christians and say to the unbelievers, “Look at that person and their unhappiness. That is what happens from getting religious. You don’t want to be like that, do you?”
Regardless of how someone falls into this condition, we need to step back and keep the evil one’s schemes in view. Satan’s tactical objective must be resisted by faith. Resist him, firm in the faith, knowing that the same kind of sufferings are being experienced by your fellow believers throughout the world (1 Peter 5:9 CSB; cf. Ephesians 6:11-18)
The evil one often appears as an angel of light. And no wonder! For Satan disguises himself as an angel of light (2 Corinthians 11:14 CSB). He comes quoting Scripture! He attacked Jesus this way (Matthew 4:6). What makes you think that he won’t use this weapon against you? Always be careful when someone throws a Bible verse at you in your struggles. People can be handing you a verse outside of its Biblical context. We must know the Bible’s storyline, as well as the immediate surrounding paragraphs of any verse. Two texts that currently suffer terrible abuse are Philippians 4:13 and Jeremiah 29:11, and the misuse of these verses can seriously complicate a person’s spiritual struggles. Why? They fail to achieve the happiness that the misuse of such verses promises, and then they blame themselves for “that one sin” of failing to believe enough or properly. People are complicated beings, and we should be careful about making the problems of others worse.
Since the prince of darkness misuses Scripture, you must have a thorough and complete understanding of the gospel. But I am afraid that as the serpent deceived Eve by his cunning, your thoughts will be led astray from a sincere and pure devotion to Christ. For if someone comes and proclaims another Jesus than the one we proclaimed, or if you receive a different spirit from the one you received, or if you accept a different gospel from the one you accepted, you put up with it readily enough (2 Corinthians 11:3-4 ESV). All of us must know that we are right with God by grace alone through faith alone in the person and work of the Lord Jesus Christ alone. Learn the letters of Romans and Galatians well. Read them and reread them.
Grace and peace, David