Wesley - The difference between vengeance and grace

Wesley taught about Prevenient Grace, Justifying Grace, and Sanctifying Grace. And even if we know about those forms of grace that Wesley emphasized, I think that we still have a hard time understanding what grace really is. I once heard it explained this way. Suppose that someone breaks into your home. In the course of a robbery, that person kills your child. If you hunt them down yourself and kill them, that’s vengeance. If you allow the police to do their jobs and the person is apprehended and punished, that’s justice. If you take them into your home and adopt them as your son or daughter, that’s grace. (Source Unknown, Lou Nicholes - Missionary/Author).