The primary purpose of the Heart is is the production of faith. The operations of the Heart demonstrate the process that produces faith. The Soul is where we put to practice our beliefs, making the Soul the testing and proving ground of our faith, or Belief System.
The Mind is the thoughtful arena where we find the adopted patterns, habits, or character of the person.
We could reduce these three systems to "Faith from the Heart", "Practice from the Soul," and "Harvest in the Mind". Though distinct, the Heart, Mind, and Soul of Matthew 22:37 are reciprocal, symbiotic, and interactive with everything we do. Insomuch, that it can be hard to isolate behavior issues in just one area.
For example, in Hebrews 4:12 we read "the Word of God ... is a discerner of the thoughts and intents of the Heart."
In Deuteronomy 8:5, we read, "You shall also consider in thine heart..."
This brings up the question is where does thought happen? We are sentient or thinking, rational beings. In additional, thought like the concept of love, has a variety of variations. The Heart is a discerning and prioritizing kind of thought that is akin to logical progression. The Soul operates as a pragmatic and functional kind of thought considers the application or actions taken. And the Mind provides a big picture, evaluation that may be more reflective and judgemental progress as a person.
Thinking occurs at various levels of the Inner Man. In this introduction, I consider the Heart quite diverse. The discernment of Heart should be our first defense concerning any issue. However, discernment is not an innate skill, but an acquired skill. A baby or infant has no discernment that is does not learn. A child will literally touch a flame until it learns that the flame will burn its fingers.
As seen in Hebrews 4:12, the instruction of the Word of God has an impact on our Soul and Heart, not mentioning the Mind. There is good reason for this. The Mind is the end of the process, not the beginning. All issues of life start in the Heart according to Proverbs 4:23. Information can be taught or collected by experience. I can tell you that the flame is hot or your can discover the information by personal experience.
Therefore, the Word of God is information. It is superior information that should be readily accepted into the Heart. There is also inferior information which should be subjected to scrutiny before accepted as having merit for your life. Inferior information ranges from absolute lies, to biases and misinformation, to something that is true as it stands. Fire is hot regardless of information to the contrary.
The Heart must filter information either "out of hand" or by further consideration of logic or discernment. Logic, however, is not often entertaining; and the Heart is capable of frivolous pursuits that need not be logical or critically considered. Given the choice of ice cream or a salad, the easy choice is ice cream. We all need and want to have fun or be entertained without worrying about the cares of the world for a while.
There is then a balance between entertainment and logic that is needed. In the considerations of the Heart, entertainment often overrides the logic of the matter. Faith must rule, and it need not rule out fun unless the fun is harmful to us. Romans 14:23 says "for whatever is not of faith is sin." This doesn't mean that we must turn into monks in a monastery. The verse instructs us that faith qualifies all else.
To boil this conversation down to a few words, discernment of the Heart is a "Faith First Principle". The many diversions and ideas we entertain must pass by the Sword of God (the Bible) for valuation. The choice to steal or not steal is a very easy determination. The decision to tithe is kind of easy. The decision to get out of debt is actually pretty hard. Yet, the Bible instructs our Heart, and the decision follows good logic. Discernment is making the best choice.