Why can't humans be happy without God?

What is the meaning of the word repent based on its context in this passage? charley knew it was his fault that the whole family had to cancel their winter vacation. it all started when he’d snuck out of his house and hid at his friend laurie's place. the whole family had spent the morning looking for charley all over the neighborhood. by the time they’d found him, it was afternoon. they had missed their flight for hawaii. now charley felt guilty for his actions. he approached his father to repent for his poor behavior. but his father would not listen to him and instead declared that there would be no vacation this winter.