The problems people face are found in either the outer man or the inner man. The inner man refers to thoughts, desires, will, emotions, as well as his spirit. The outer man is the physical—that part of man that is subject to decay. 
Therefore, we do not lose heart, but though our outer man is decaying, yet our inner man is being renewed day by day. 2 Corinthians 4:16 (NASB)
All the aspects of the inner man are captured by the word “heart.” Thayer’s Greek Dictionary defines heart like this:
2b1) kardia-the soul or mind, as it is the fountain and seat of the thoughts, passions, desires, appetites, affections, purposes, endeavours 2b3) of the will and character 2b4) of the soul so far as it is affected and stirred in a bad way or good, or of the soul as the seat of the sensibilities, affections, emotions, desires, appetites, passions.
From these considerations we can clearly see that the heart and soul are one and the same thing, and by no means is the word “heart” confined to mean, “how we feel.” What makes matters worse is that when we trust our feelings in order to make decisions or “speak truth to us” we often rationalize sin. For example, how many Christian divorces have taken place because the feeling of love is not what it used to be? How many Christians equate feelings of sadness with, “I must be sick or have some sort of depression disorder?” How many people make decisions based on the fuzziness of “following your heart?”
For example, as a biblical counselor I have had people tell me they have made a certain decision because they prayed about it and, “had a peace in their heart.” This is the Christian version of following your heart. A couple of examples I’ve seen are starting a business that failed or making a move that bordered on the irrational.
The language reflects a subjective, experiential, feelings-approach to life rather than a solid, scriptural approach to life.  
A biblical understanding of the heart is necessary before we can understand how to change to glorify God. But we also need to understand our true heart’s condi­tion so that we see our desperate need for a Savior and His righteousness.
It is very popular today in many churches to say that man (and his soul) is basically good. The notion that man is basically good is perpetrated in the church by a psychologized gospel that exalts man. One popular poll asked professing evangelicals if man was basically good or bad. The astounding results showed that 77% believed man was basically good. Perhaps we should not be surprised by this as many preachers are preaching messages that are based on making people “feel good” about themselves.
Man was created by God in His image. The Scripture teaches that man was cre­ated sin-free and has a rational nature, intelligence, a will, and moral responsi­bility (Gen. 1:26-28). But being created in the image of God does not mean that man is basically good by nature.
Adam and Eve disobeyed God and lost their innocence (Rom. 5:12). Man was guilty of sin and incurred the penalty of spiritual and physical death becoming subject to God’s wrath because God cannot tolerate sin. Man then became in­herently corrupt and totally incapable of choosing or doing that which is accept­able to God apart from divine grace (Rom. 5:19). Man, thereby, has no power within himself to recover and is hopelessly lost. Historically, this radical cor­ruption of the soul has been called “total inability.”
Wayne Grudem notes in his commentary on Ephesians 4:18 that total inability does not mean that every person is as bad as he or she might be, for God’s common grace restrains unredeemed sinners from fully realizing their sinful potential. Every person has the potential for even the worst of sins, since every aspect of a person was affected by the fall (will, emo­tions, thoughts, etc.). Scripture (see Romans 12:16) indicates we are inclined to think too highly of ourselves and our “goodness.” We are more prideful than we want to believe!
We find the true condition of the heart in Scripture.
Then the LORD saw that the wickedness of man was great on the earth, and that every intent of the thoughts of his heart was only evil continu­ally. Genesis 6:5 (NASB)
This is one of the strongest and clearest statements about man’s sinful nature. The people of Noah’s day were exceedingly wicked from the inside out. Why? Because the fall affected every aspect of the heart.
The heart is deceitful above all things, and desperately wicked; Who can know it? Jeremiah 17:9 (NKJV)
The prophet Jeremiah declares the heart is deceitful above all things and desper­ately wicked. At the very least it means our hearts cannot be trusted. Yet, in our culture we constantly hear from psychology that we are to follow our hearts, make the right heart choice, or are told your heart can be trusted to guide you.
When these things are said, they are, in fact, equating feelings with the heart. Clearly, that notion is contradicted directly by what God says – do not trust your heart emotions because they are deceitful and cannot be trusted to lead you.
For from within, out of the heart of men, proceed the evil thoughts, for­nications, thefts, murders, adulteries, … Mark 7:21 (NASB)

Think about these things…this may be the first time you have heard these truths and perhaps this has rocked your world! Be a Berean and study these things, and learn what the Bible says about the heart. This is the first step toward true and lasting change in your life!