God is greater than our heart.

Jeremiah 17:9 says, "The heart is deceitful above all things, and desperately sick; who can understand it?" Hear what Martin Luther has to say about speaking to one's own heart...

"From our own (guilty) conscience certainly only accusing thoughts can come, because our works are vain before God, unless He himself is [effective] in us by His grace. We, of course, may easily excuse ourselves. But that does not mean that we have satisfied God or fully kept His Law. But from whom, then, do we obtain the thoughts that (truly) excuse us? Only from Christ and in Christ; for if the conscience of a believer in Christ reproves, accuses and condemns him as an evil-doer, he quickly turns from himself to Christ and says: 'He has atoned my sins. He is just and my Justifier, who died for me. He has made His righteousness my own and my sins His own. But if He has made my sins His own, then I no longer have them but am free from them. And if He has made His righteousness my own, then I am righteous because of His righteousness, for He is God, blessed forever.'

So, then, 'God is greater than our heart' (1 John 3:20). Far greater is He who defends me than that which accuses me, indeed, infinitely greater. God is my Defender, while my heart is my accuser. Oh, what a blessed relation! But so it is, just so! 'Who shall lay anything to the charge of God's elect?' (Romans 8:33) No one! Why? 'It is God that justifies! Who is he that condemns?' No one! Why? 'It is Christ (and He is God!) that died, yes rather, that is risen again, who is even at the right hand of God, who also makes intercession for us.' In short, "If God be for us, who can be against us?''' - Martin Luther, "Commentary on Romans"