I have always thought that Grace is solely the heart disposition of God toward man. Lately i realised that it goes beyond that. Paul would say I commend you to GOD the, word of Grace which has ability or power to build. Just as Romans describe the gospel as being the power of God to salvation, so was Paul describing God Grace as God's power to transformation.
Grace triumphs over the devil and makes anything he can do to you null and void. Because of grace, not because we earned it or deserve it, but because it is a gift from God; God's greatest gift.

Indeed Grace is what we preach. It is the Gospel we preach showing or revealing both God's heart and Gods power.