One of the most dangerous challenges we face comes from within us: our heart. This governs our approach and attitude toward living the life we have been given. When we find ourselves in a wrong attitude or desiring wrong things, it serves as a reminder to stop and consider which heart motivates us. We must guard the new heart that God is trying to give us, for the old heart, our former way of thinking and acting, profits us nothing. If we choose not to hear God's Spirit urging us to pray, study, fast, meditate, and obey, putting God first in our lives, then our heart will slowly become hardened. God's Word and way of living will lose importance. We must not allow our hearts to become hardened, lest we drift away from the foundation of our confidence and the path we are called to follow. Our forefathers erred in their hearts, setting them on the lust of the eyes, the lust of the flesh, and the pride of life, going astray first in their hearts. We are warned not to be like those who came out of Egypt, who saw the miracles and awesome power of God, yet rebelled against Him and died short of the rest set aside for them. The error always stems from the heart, and we must strive to prevent it from hardening, rejecting the new heart that God is working to give us.

The heart is a central and vital element of our spiritual existence, often used metaphorically in Scripture to represent the inner person, encompassing the mind, emotions, will, and sinful nature. It is mentioned numerous times across various translations, highlighting its importance, as God is deeply concerned with the condition of our hearts and minds. The heart's deceitfulness is evident, as it can be easily deceived and desperately vulnerable, prone to deception and wretchedness beyond all things due to the wickedness within it. God searches the heart, testing the deep things within a person to give each according to their ways and the fruit of their doings. Our actions and deeds, whether good or bad, proceed from what is inside our hearts, revealing who we truly are. While people may look on the outward appearance, God is always concerned with the reality and condition of what lies within us. Therefore, we must guard our hearts with all diligence, for out of them spring the issues of life, ensuring that we keep them pure and clean to respond positively to God in all situations.

The heart, as described in Jeremiah 17:9, is deceitful above all things and desperately wicked, portraying a nature that is inherently fraudulent and corrupting. It is characterized by prideful vanity, a self-serving attitude that intentionally perverts truth to mislead others into surrendering something of value. This deceitful heart appears attractive on the surface, yet its appeals are lies, dangerous and incurable in its ways. God views this heart as something foul, belonging in the sewer, an entity so hardened that truth struggles to penetrate it, likened to a heart of stone. Only through God's intervention, by granting a new heart of flesh that yields to His way, can this condition be remedied. This deceitful heart poses a significant barrier to fulfilling the two great commandments of loving God with all one's heart, soul, and mind, and loving others as oneself. Its self-centered nature renders consistent obedience to these commandments impossible, preventing the development of character valuable to God's kingdom. The heart's narcissistic tendencies drive expressions of evil, intensifying as cultural moral standards decline, pulling individuals into sinful behaviors through a mob mentality. These characteristics, evident in qualities such as self-love, covetousness, pride, and ingratitude, among others listed in II Timothy 3:1-5, are inherent in human nature and present even within the church, posing a constant threat of drawing individuals back into self-absorption. The deceitful heart's influence is tragically visible in the church, as seen in the Laodiceans of Revelation 3:14-18, where converted individuals, still possessing God's Spirit, allow their carnal heart to regain control, turning their attention away from Christ to self-centered interests. This heart convinces them they no longer need what He offers, believing themselves spiritually rich, thus rejecting Him through their conduct. These expressions of human nature, described as elements of mental illness from God's perspective, must be challenged and overcome through the power of His Spirit, which provides a sound, disciplined mind to control and subdue these ungodly traits.