To harden one's heart is to give one over to their own desire seal them in it and where they get no pleasure, satisfaction out of it. God gives them over to their own evil desire. What comes from God is good, what comes from not God is not good. That is why man can do evil because they are not God and they are a free agency. If they were not a free agency they could not disobey God. It is because man is granted a free agency that they can disobey God. Man on their own do evil if motivated other than by God, because it is motivated by their own desire. That is why Jesus the Son of Man said not my will but your will be done. Jesus the Son of Man learned Hebrews 5:8 Son though he was, he learned obedience from what he suffered Jesus the Son of God knew everything. There is a foolish notion that if God does evil it is good. If God did evil and said it is O.K. because I am God so it is good. He would not be god but the anti-Christ and many will be mislead by him, even very intelligent men. Those who use their intelligent to make God's word what they want it to say. That is how I see harden heart, how would you describe it?