How do we know that God's grace changes our nature?

According to Ephesians 4:20-24, if you have learned Christ and been taught by Him, you are given a new nature that desires to seek Him. This new nature empowers you to recognize your sinfulness and need for a Savior, while also enabling a shift in behavior. The presence of this new nature indicates that a genuine work of grace has occurred in your heart, evidenced by a desire for righteousness that is not present in the unregenerate. The struggle against the old nature signifies that there is indeed a new nature, one that responds to God's grace with a desire to live according to His will.