Jared Wilson points out that "The full Gospel is not Christ atoning for us and then us doing good works; the full Gospel is Christ atoning for us and then reconciling us with each other." Jared goes on to explain:

This may sound like a distinction without a difference, but it really is different. It is the difference between seeing the Sermon on the Mount as merely "stuff to do" and seeing it as "stuff to be." The Sermon on the Mount is good news not so far as it is giving us a new law, but in so far as it announces that under this new law the poor in spirit are blessed, the meek will inherit the earth, those who hunger for righteousness will be satisfied, etc.

This is why the Gospel is news, not advice.

(HT: Transforming Sermons - Milton Stanley)