Following Jesus is tough, we have to both put aside sin while also trusting Jesus. Plus we're all works in progress, facing different types of problems. While we were still enemies God extended grace to us, inviting us into the relationship of the Father and the Son. But a relationship isn't static, if we trust Jesus we'll respond with obedience.
You could say one of the features of Bonhoeffer's theology was a type of radical discipleship, an emphasis on the way the disciples of Jesus work out their salvation together. Just as grace was extended to us we extend grace to each other. And just as we're in a relationship with God, we're in relationships with one another. One of the big emphasis of the New Testament is "one-anothering", we love, serve and forgive one-another. God works out the doctrines of grace in our lives though prayer, preaching and other people.
So it can be tempting for Christians in conflict to demand grace, without the costly process of negotiation and self-reflection. Conflict is part of this world, there's no escaping it. However the disciples of Jesus work inside God's grace, work at solving problems and disagreeing positively within a mutual relationship with each other and God. Grace isn't something to be wielded by the aggrieved party to leverage compliance. The different aspects of following Jesus; repentance, compassion, patience, self-sacrifice etc shouldn't be used to gain power over the other followers of Jesus.
Psychologically we have sympathy for the oppressed. Spiritually it makes sense if you've been forgiven to forgive others at the drop of a hat. However, Bonhoeffer's neologism is a useful reminder that true grace is costly. If you're in the midst of a conflict, negotiating something difficult, it can be confusing to be told 'to show grace', 'be more loving' or 'have more compassion'. No doubt if you live on this earth you should be more of all those things, we're all works in progress. However, discipleship is about working out things together, seeking the best for each other. Don't weaponise grace and don't let it be weaponised against you.