Deuteronomy 4:29-31:  If [even after worshipping idols] you will seek the Lord your God, and you will find Him, if you seek Him with all your heart and soul. When you are in distress, and all these things come upon you .  .  . when you turn to the Lord your God and obey His voice (for the Lord your God is a merciful God), He will not forsake you nor destroy you, nor forget the covenant of your fathers which He swore to them.

What does it mean, ‘With All Your Heart”?  Yes, I know, it means that you’re really serious; that you really want to have a relationship with God; that you want the benefits of having a close relationship with Him, because what you’ve been doing definitely isn’t working.

Sounds like, from the next sentence, that if you’re tired of going on without God, and you’ve done a whole lot of really stupid stuff, (like worshipping something besides God), and all these [bad] things come upon you .  .  . when you turn to the Lord your God and obey His voice.  .  .  God won’t forsake you or destroy you or forget the covenant He made with your fathers, because He is a merciful God.

So what God wants is for you (and me) to turn back to Him and obey what He says.  The turning back and obeying is evidence of what is going on in your heart, evidence of a change of your heart.

But what God really wants is that you’re actually going to give up and let God have His way with you and your life; that you’re going to surrender totally and let God have control of your life.  Are you ready for that?  It’s no half measures; it’s throwing all your cares on Him because He cares for you. It’s trusting Him so much that you don’t care what happens or what it looks like to the world, you’ve decided to let Him take care of it and of you.  It’s knowing in your heart that God really CAN take care of you better than you can take care of yourself.

One last thing: God knows whether you’re doing it “With All Your Heart”, because He’s looking at your heart; not at external appearances.