Deuteronomy 1:41 (ESV)

41 “Then you answered me, ‘We have sinned against the LORD. We ourselves will go up and fight, just as the LORD our God commanded us.’ And every one of you fastened on his weapons of war and thought it easy to go up into the hill country.

The Horeb generation made a belated attempt to go into the land, which at one level sounded right: it included a confession of sin, and a resolve to go up and fight in obedience to the Lord. But this was inspired by a momentary confidence that was itself brought on by a realization of how consequential their rebellion against the Lord was. Their trust was superficial, and with that shallow trust they forgot just how difficult their task was.