What does John 3:10 mean?

There are times when the most loving thing you can do for another person is remind them that they are not perfect. Nicodemus was a well-educated, wealthy, powerful person. In the last few verses, Jesus has told him that this is not enough to earn him the kingdom of heaven. Instead, Jesus tells him that he needs to be "reborn" through the Spirit. Nicodemus is honestly seeking answers, unlike many of the other Pharisees. He sought out Jesus (John 3:1), and correctly interpreted His miracles as signs from God (John 3:2).

And yet, Nicodemus' legalistic mindset won't let him accept the ideas that Jesus is teaching. So, Jesus puts a hole in his self-image. In the Greek, Jesus literally refers to Nicodemus as "the" teacher of the Jews. Nicodemus must have been a particularly knowledgeable man, and he certainly studied the Old Testament in depth. But there is a large difference between knowing facts, and understanding truth. Jesus meets Nicodemus right at the point of his need: by breaking up his self-reliance. This is a strong contrast to the woman at the well, from chapter 4, who needs to be lifted up and encouraged.