They did not realize they were storing up wrath
Jesus spoke a parable of a vineyard owner who leased his vineyard to vinedressers, and then went away for a long time.
At vintage-time, he sent servants to reap some of the harvest, but the vinedressers beat the servant and sent him away empty-handed, and the owner sent a second servant with the same results. Jesus said further,
“And again he sent a third; and they wounded him also and cast him out” (Luke 20:12).
This led them to believe that they had the upper hand and that they could take advantage of whomever the owner sent, but the owner was showing compassion on the vinedressers for what they had done, and the next thing they would do, would bring harsh wrath upon themselves.
We believe that we have gotten away from sin, but we may only be storing up wrath for ourselves.