Hardness of heart is the progeny of anger, which, almost assuredly, develops incrementally through choices you make. This is one example of how the Sovereignty of The Most High and the free will of men play out. The unregenerate is compelled to the works of the flesh including anger ...
(Galatians 5:19–22),
And the works of the flesh are well-known, which are these : adultery, whoring, uncleanness, indecency, idolatry, drug sorcery, hatred, quarrels, jealousies, fits of rage, selfish ambitions, dissensions, factions, envy, murders, drunkenness, wild parties, and the like – of which I forewarn you, even as I also said before, that those who practise such as these shall not inherit the reign of Alahiym. But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, trustworthiness, gentleness, self-control. Against such there is no Torah. And those who are of Mashiach have impaled the flesh with its passions and the desires. If we live in the Spirit, let us also walk in the Spirit. Let us not become conceited, provoking one another, envying one another.
...whereas the called out assembly can draw on the power of the RUACH HaKodesh to resist fleshly temptations. Failing to deal with anger, the believer yields himself or herself to demonic purposes, which the Apostle Pa'al describes…
“Be wroth, but do not sin.” Do not let the sun go down on your rage, nor give place to the devil.
Eph`siyim (Ephesians) 4:26-27
Please be advised: angry followers paint a target on their back for the demonic realm to take their best shot at! The Apostle Pa'al also explains how to deal with the state reached by remaining on this path…
For though we walk in the flesh, we do not fight according to the flesh. For the weapons we fight with are not fleshly but mighty in Alahiym for overthrowing strongholds, overthrowing reasonings and every high matter that exalts itself against the knowledge of Alahiym, taking captive every thought to make it obedient unto Mashiach,
Qorintiyim Bĕt (2 Corinthians) 10:3-5
Having covered the beginning and the end, let’s examine intervening steps. Prolonged anger fuels impatience and leads you to believe your rights were violated, Alahiym is indifferent, you are exempt from pitfalls and must deal with the situation. This leads you to rationalize your position and fantasize how to orchestrate various outcomes. “Well, I don’t deserve this! I have a right to defend myself!” And yonder you go, playing on Satan’s courtyard. You follow like rail cars on a track with justification of your feelings, thoughts and plans, departing yet further from the Scriptural directive. “You know, if I don’t do something, this person will do it again.” And the plot thickens. Justifying yourself diminishes your sensitivity to reproof, and you may be in denial. On the silver screen of your mind, picture a new–baby’s foot, along side the foot of an elderly tribesman, who never wore shoes in his life. The tribesman’s foot callous allows him to traverse harsh terrain without pain or injury. Spiritual callous equips you to traverse trying times ambivalent to the quickening voice of the Ruach Ha'Kodesh. Appealing to someone having a hardened heart in the latter stages is like reasoning with a pack mule. According to Yahusha in Mark 8:17, hardness of heart distorts your logic, like playing solitaire with a deck of fifty-one. Spiritual callous diminishes your ability to receive reproof, which is why II Corinthians 10:3–5 is vitally important. The Mashiach gave you a prescription for dealing with trespasses against you…
“And if your brother sins against you, go and convict him, between you and him alone. If he hears you, you have gained your brother. But if he does not hear, take with you one or two more, that ‘by the mouth of two or three witnesses every word might be established.’ “And if he refuses to hear them, say it to the assembly. And if he refuses even to hear the assembly, let him be to you like the nations and a tax collector.
Mattithyahu (Matthew) 18:15-17
Scripture is just not that hard to understand, but it is incredibly challenging to obey. Your flesh will scream out with an alternative plan at every turn. There's never a shortage of distraction. You alone, can, and must, deal with the flesh in your life. When you hold on to something like anger, you invite the work of Satan, and he always pays off in counterfeit bills. If you walk in the spirit in you will not fulfill the lusts of the flesh (Galatians 5:16).