Satan is an expert at rubbing our noses in our past sins. He knows how to plague Christians by telling them their sins are so great they should despair. He masks the truth (“You have sinned greatly against God in thousands of ways…”) with a lie (“…Therefore you have no hope of salvation”). Puritan Thomas Brooks (d. 1680) said that this is one of Satan’s wicked devices to keep Christians away from Christ: He suggests to the soul the greatness and vileness of his sins. Brooks also gives biblical remedies for this wicked device of Satan. Here are four (of eight) remedies (summarized/edited):
1) The first remedy against this device of Satan is to consider that the greater your sins are, the more you stand in need of a Savior. The greater your burden is, the more you stand in need of one to help bear it. The deeper the wound is, the more need there is of a surgeon. The Christian says: ‘The greater my sins are, the more I stand in need of mercy and pardon, therefore I will go to Christ, who delights in mercy, pardons sins, and is able to forgive beyond imagination” (Mic. 7:8, Is. 43:25).
2) Another remedy against Satan’s wicked device is to remember that the promise of grace and mercy is to returning souls. You are never so wicked, if you return to God, that he will be yours, mercy will be yours, pardon will be yours: ‘For the Lord our God is gracious and merciful, and will not turn away his face from you, if you return unto him (2 Chr. 30:9). See also Jer. 3:12, Joel 2:13, and Is. 55:7. Christ’s heart and arms are wide open to embrace the returning prodigal.
3) Consider that the greatest sinners have obtained mercy, and therefore all the angels in heaven, all the men on earth, and all the devils in hell cannot testify to the contrary, that you are able to obtain mercy. Consider Manasseh, Paul, and Mary Magdalene. Christ still hangs out a white flag of grace and mercy to returning sinners that humble themselves at his feet for favor.
4) The fourth remedy against this device of Satan is to remember that everywhere in Scripture Jesus welcomes the worst of sinners that are willing to receive him and rest upon him for happiness and blessedness. Those that come to him he will not cast out, be they ever so filthy, sinful, unworthy, or rebellious. Oh sinners, tell Jesus that he since he has not excluded you from mercy, therefore you are resolved to sit, wait, weep, pray, and knock at the door of mercy until he says to you, ‘Be of good cheer, your sins are forgiven, you are justified, and your soul shall be saved.’ See also Heb. 7:25.