Confusion leads to pain.
The way you talk about something will either lead to health or increasing pain. There's growing scientific research to suggest that our thoughts [and therefore the way we talk about them] actually have resonance at the subatomic level, something like a signature or substance that moves through time and space affecting the molecules around them. [See Quantum Theory]  We know that sound waves move the air and molecules around them. Now we're discovering that our prayers and thoughts do as well. Let's assume how we talk [based upon those thoughts] also carries actual creative power.
Thoughts create. Talking that flows from those thoughts creates. The wrong thoughts and talk create pain.
Why does it matter how we refer to the heart?
Most Christians refer to entirety of their inside world as their "heart." Every thought, every emotion, every temptation, every desire gets lumped into the melting pot of their insides, and they call that vast mixture their "heart." Whether bad or good, they mistakenly call everything that takes place deep inside them, their "heart."
It is not so.
When we open the hood of our car, we would never refer to everything we see there as "the engine" because there's also the battery, hoses, and sparkplugs. The engine is but one thing you see under the hood. But because we can't "see" our mind, body and 'flesh;' or take an x-ray of our spiritual insides, our habit of lumping them all together has left us painfully confused.
That's why you can hear a pastor say on one Sunday that he believes we are "new creations" regenerated by the Holy Spirit, but out of his lips next Sunday he carelessly prays, "Let your light come into our darkened hearts this Christmas season." How can you be a "new creation " -- having the new heart God promised through Ezekiel and Jeremiah and affirmed in the New Testament -- yet assume that a Christian's heart remains a darkened heart? No wonder Christians are confused!
Sorting it out
The heart is only one part of our insides, and if we get that wrong, we'll believe that all sorts of terrible thoughts and desires are coming from our heart when they're not.
As Christians, our new heart is only one source of thoughts, emotions, and desires within us. The mind is another; so is the "flesh," that ghost remnant of our former lives. We also have an Enemy outside of us that loves whispering half-truths to us, then blaming us for buying into them.
Only good fruit can come from good roots.
Your new God-given heart [the rootedness of your new identity] can only produce good fruit. So when we speak of any kind of temptation, wayward desires, or addictions swirling around our insides, we must no longer think that all of that mess constitutes the heart or comes from it. No. The mess comes from anything BUT the new heart God gave us when we said 'yes' to Him.
Bottom line: Your new heart isn't the problem. The new heart is the new wineskin for the Spirit. Let's not lump everything inside us under one label, because confusion is painful.
 UpperDogs, Sarah Thiessen & Heather Hughes. The authors, both Christians devoted to restoration, make a compelling case that Quantum Theory provides evidence that both our thoughts and our prayers, especially under partnership with the Holy Spirit actually create new realities.