The gospel is the good news that in Christ we have been given the very righteousness of Christ himself. This means that everything God commands of us is given to us in Christ as a gift.
When we talk about bettering ourselves, we need to realize that a theology of the cross does not militate against this endeavor but that it places it squarely in the horizontal realm.
As sinful humans, we are adept at taking what God gives as gift and making it into a work. Nowhere is this made more evident than in the universally misunderstood doctrine of sanctification.