About the law of God in your heart:

Psalm 37:30 The mouth of the righteous man utters wisdom, and his tongue speaks what is just. 31 The law of his God is in his heart; his feet do not slip.

If we want to be who Christ wants us to be then we will be righteous at all times and in all matters. When we seek to be righteous we must also seek to be wise. When we are righteous we speak rightly and wisely. When we are righteous we speak in favor of righteousness and doing the right thing. When we are righteous we speak in favor of what is just. In righteousness, let the law of God live in your heart for from His law blossoms abundant life. When you live a righteous life, living out God's law gives you a sure footing in life, meaning you do not slip or you do not fall.

Living in righteousness means we live the law of God. Living the law of God means we only want what Christ wants. Living in righteousness means all of what God wants us to be is who we are. Living in righteousness does not mean we only speak the words of the law. Living in righteousness does not mean we speak just a mindless repeating of scripture verses, nor does living in righteousness mean we do human memory feats with the words of God. Living in righteousness means, in our life, there is for us a total living out of what God wills.