"But the Lord said to me, 'Tell them, "Do not go up and fight, because I will not be with you. You will be defeated by your enemies."' So I told you, but you would not listen. You rebelled against the Lord's command and in your arrogance you marched up into the hill country." NIV translation
Moses informed the people that God had made up His mind and that they were facing defeat if they tried to go against His word. He had already decreed that none of them would see the land.
In the same way, God has given us His word which tells us how we can live in this world and still glorify Him. We cannot have possession of the life that He desires for us if we are unwilling to listen to and follow His word.
"The Amorites who lived in those hills came out against you; they chased you like a swarm of bees and beat you down from Seir all the way to Hormah." NIV translation
The Israelites tried to take the land but were soundly defeated by the Amorites just as God had said. In the same way, we can try to walk in this world on our own but we can expect the same result as Israel had. It is arrogant of us to think that we can do anything on our own. We must be humble enough to admit that we need the Lord's guidance for all things.
"You came back and wept before the Lord, but he paid no attention to your weeping and turned a deaf ear to you. And so you stayed in Kadesh many days - all the time you spent there." NIV translation
The Israelites wept before the Lord but still did not want to humble themselves enough to accept the words of God. The first step to being right with God is a repentance which is acknowledging that you are headed in the wrong direction.