Then he said to his slaves, 'The wedding is ready, but the ones who had been invited were not worthy. So go into the main streets and invite everyone you find to the wedding banquet.' And those slaves went out into the streets and gathered all they found, both bad and good, and the wedding hall was filled with guests. But when the king came in to see the wedding guests, he saw a man there who was not wearing wedding clothes. And he said to him, 'Friend, how did you get in here without wedding clothes?' But he had nothing to say. Then the king said to his attendants, 'Tie him up hand and foot and throw him into the outer darkness, where there will be weeping and gnashing of teeth!' For many are called, but few are chosen." (Mat 22:8-14)
This man had been called by God to salvation. He had even accepted the invitation -- he believed the Gospel. He even made the effort to show up at the banquet.
But he made no preparations before God.
Just like the five virgins in Matthew 25:1-13 who were waiting for the bridegroom but ran out of oil, he was left in the outer darkness, cut off from God for all eternity. It is preached by many today that you need only accept Jesus into your heart, but there are many warning such as this one that simple belief or even confession of faith is not proof of genuine conversion.
Then Jesus said to his disciples, "If anyone wants to become my follower, he must deny himself, take up his cross, and follow me. (Mat 16:24)
Salvation is more than just accepting Jesus Christ; we must follow Him too.