Hardening is like a callus or like the tough bone fibers that bridge a fracture. Spiritual hardening begins with self-sufficiency, security in one's self, and self-satisfaction. The real danger is that at some point, repeated resistance to God will yield an actual inability to respond, which the Bible, describes as a hardened heart, insensitivity indicates advanced hardening, Heer are som of the warning signs.
Disobeying - Disobedience leds to his hardened heart - Exodus 4:21
Having wealth and propserity - Taking God's blessings for granted can cause us to feel as if they were owed to us - Deuteronomy 8:6-14
Rebelling and being discontented - Suffering or discomfort can create an attitude that blames God - Psalms 95:8
Rejecting - Rejecting God's gift makes our neck stiff and our hearts hard - Proverbs 29:1
Refusing to listen - Refusing to listen leads to a loss of spiritual hearing - Zecharia 7:11-13
Failing to respond - Listening to God with no intention of obeying produces an inability to obey -Matthew 13:11-15