I once attended a conference on healing and deliverance and one of the things I saw is how the enemy uses a person's wounding and past hurts to persuade them to harden their hearts.
Like a person who is injured physically and develops a scab at that place of hurt eventually, so the same thing can happen to your heart.
The enemy can convince you that hardening your heart is necessary to protect you from further hurt.
If a person has a hard heart, they won't believe God’s love. Believing God's love puts them in a position of vulnerability and humility, which scares them.
They also won't receive God’s word because it can't penetrate through a hard heart. Or if it does, the Word won't go very deep!
In the following article are some truths about Jesus that can help soften the hard heart – if the person will believe.
I also included my prayer for a person suffering from a hard heart in the article.