Because so many of our sins flow from a basic doubting of God’s goodness to us, trying harder and beating ourselves whenever we fail often doesn’t change our pattern of behavior. For it doesn’t deal with the root problem, the big sin behind the surface sins: our failure to believe that God is really good. In fact, the more pharisaical we get in our approach to life, the more we become convinced that God isn’t really good. How could God really want the best for us, and then load us down with all these rules and regulations?
The real answer to sin is the gospel. It is remarkably straightforward. You need to look at Jesus on the cross and focus on the exchange that was transacted there. My sins were loaded on him, while his perfect righteousness was given to me. When I set that reality clearly before my eyes and understand it in my heart, how can I doubt that God is good? The road to joy-filled obedience begins when this great truth dawns on us: “He who did not spare his own Son, but gave him up for us all – how will he not also, along with him, graciously give us all things” (Rom. 8:32).Iain M. Duguid
Living in the Gap Between Promise and Reality, page 116