Have you ever seen someone who doesn't even want to try a task, but still says "I already know how to do it, you don't need to teach me"? It's funny, because usually the person who says that knows the least.
The Bible tells about a kind of lazy person who thinks he's wiser than seven smart people put together. Seven is a number that means "a whole lot of really good people." But that lazy person doesn't want to listen to anyone's advice, because he thinks he already knows everything, even without ever really trying.
Think about a new game, or a subject at school. Sometimes we don't want to practice, don't want to study, and still want to look like we've already mastered it all. The truth is, nobody gets good at anything without effort and without listening to those who already know more. The truly wise person is the one who recognizes "I still have things to learn" and asks for help.
Jesus, even though He was the wisest of all, always valued those who had the humility to learn. He said that the Kingdom of God belongs to the little ones, to those with a simple heart ready to listen and grow, not to those who think they're too wise to listen to anyone.
Whoever thinks he already knows everything is the one who learns the least.