Matthew 18 is chock-full of grace for the struggling sinner - and for our how sinners treat struggling sinners. The chapter is to be read as a whole. It begins with humility and temptation (1-6), and it ends with what we do with those who give in to temptation (21-34).
The central force of the whole is the God in the middle (10-14). This is a God who does not despise the wanderer - whether it be you or the other guy. Instead He leaves the 99 who are near to hunt down and find that wandering sheep, even at great cost (12). How far did Jesus travel, from the throne of heaven, to a manger, and a carpenter’s shop, and a cross? Yet he did this for joy - “. . . For the joy set before him, he endured the cross” (Heb. 12:2). That joy was bringing that lost sheep home. The Father does not will that any of His children should perish (14).
So then, when you are the wandering sheep, deal with the sin with the violence that it would lead you to (7-9). It wants to lead you to the fire of hell (9), so throw it away, where it came from. Let the old parts of you be lopped off and thrown back in the grave.
But when it’s the other guy (and we will all be on both sides of this), Jesus stipulates a procedure to follow (15-20). This section is often referred to as “church discipline,” but that’s not quite right. Because the goal here is the same as the Father’s goal in v. 10-14 - reconciliation. Sin alienates, but grace reconciles. Sin divides, but mercy unites again. So we follow this procedure, as difficult as it may be, not because we hate, but because we love.
Verses 15-20 are about bringing the unrepentant to repentance. But what about the repenter who struggles, whose struggle with sin resembles a dead cat bouncing after being thrown out of a short building? A lot of grace; a lot of forgiveness (21-35). Which is no more than what the God in the middle gave to us (27). We are to remember what we’ve been forgiven of - an infinite, unpayable debt (24) - and forgive the one who has harmed us much less (28). Do the math, Jesus says.
Forgiveness is rarely easy. It is a form of suffering. But we rarely look more like God than when we forgive. Forgiveness is very much an either-or moment. Either we glorify God, or we de-glorify Him. There is no middle ground. So keep short accounts. Confess sin, and forgive, forgive, forgive.