In the simplest of terms, what God wants from you is your heart. Some might hear that and think it’s the basis for a kind of sentimental religion. Others hear it and conclude that if God wants our hearts He is asking for an easy thing. But God asking for our heart, above mere behavior and agreement, is the greatest demand He can make. Asking for a man's heart is asking for all of the man, not just part.
Everything that really matters in life is done with the heart. Without the heart whatever we do is ultimately useless and fruitless. God is grieved when we "draw near" to Him in word while retreating from Him in our hearts (Isaiah 29:13). And because in all things at all times God wants our hearts we are cautioned to keep the heart (Proverbs 4:23) and "direct" it in the way.
Hear, my son, and be wise,
and direct your heart in the way.
(Proverbs 23:19 ESV)
The easiest mistake to make in our spiritual life is to focus on external behavior while neglecting the internal aspect of the heart. And to neglect heart work is to risk spiritual ruin.
Consider that giving thanks, rejoicing, singing, and of course loving, is all heart work (Psalms 9:2; Psalms 13:5; Ephesians 5:19; 1 Timothy 1:5; 1 Peter 1:22). Do you understand that faith and repentance, to be genuine, must stem from the heart (Romans 10:9; Psalms 51:17)? Do you know that the greatest danger you face as a Christian is unbelief stemming from a hardened heart (Hebrews 3:12)? This is why Scripture calls us to direct our hearts in the way.
The Heart is Strengthened by Grace
Before we get to anything we can do in guiding our hearts, it is important to understand that the strengthening of our hearts is a work of God and the result of His grace. As it says in Hebrews, "it is good for the heart to be strengthened by grace." (Hebrews 13:9) Heart change is a divine work that cannot be forced or bought. It is a gift that God gives to everyone who believes in Christ. In fact, the New Covenant promises heart transformation.
And I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh. And I will put my Spirit within you, and cause you to walk in my statutes and be careful to obey my rules.
(Ezekiel 36:26 ESV)
Those who receive Jesus are made new creatures (2 Corinthians 2:17), are given new hearts, and the consequence is growth in godliness. God promises to renew and strengthen the heart of all who believe in the Son. This is foundational. There is no transformation apart from grace. And yet the degree to which we grow in that grace is largely dependent on how we direct our hearts.
The Heart is Directed by The Word
To direct the heart is to guard it from danger and guide it to Jesus. And the God-given means by which we can do this is His word.
How can a young man keep his way pure?
By guarding it according to your word.
With my whole heart I seek you;
let me not wander from your commandments!
I have stored up your word in my heart,
that I might not sin against you.
(Psalms 119:9 ESV)