If today you hear God's voice, harden not your hearts (see Ps 95:7-8).
We can have hardening of our hearts for years, even for generations (Jer 7:26). For centuries, we can ignore God and become progressively worse than our fathers, who were worse than their fathers and grandfathers (see Jer 7:26). The hardening of hearts can be chosen not only by individuals but by nations (see Jer 7:28). Hard and hardening hearts can be generational, epidemic, deteriorating, and international. They can become so hard that we kill God's prophets, forget that there is faithfulness (Jer 7:28), accuse Jesus of working for the devil (Lk 11:15), become pawns of the devil, kill millions of babies in the womb, constantly watch sin on TV for entertainment, never bother to read the Bible, rebel against God's Church, and be involved in other related perversions, self-deceptions, and atrocities.
If today you hear God's voice, harden not your hearts.