A) Fallen man hates the Light and will not come to it.
John 3:19,20 (Webster)
19 And this is the condemnation,
that light is come into the world, and men have loved darkness rather than light, because their deeds were evil.
20 For
every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.
Contrast that with someone who has been born of God.
John 3:21 (Webster)
But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God.
B) Fallen man is hostile to God and cannot please him (repentance and faith please God).
Rom. 8:7,8 (Webster)
7 Because
the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be. {the carnal...: Gr. the minding of the flesh}
8 So then
they that are in the flesh cannot please God.
Again, contrast this with someone who has been born of God.
Rom. 8:9 (Webster)
But ye are not in the flesh, but in the Spirit, if the Spirit of God dwelleth in you. Now if any man hath not the Spirit of Christ, he is not his.
C) This is why Jesus told Nicodemus that you (plural) MUST be born again, in order to see and enter the kingdom of God. We enter the kingdom of God, through faith in Jesus Christ.
John 3:3-7 (Webster)
3 Jesus answered and said unto him, Verily, verily, I say unto thee,
Except a man be born again, he can not see the kingdom of God.
4 Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother’s womb, and be born?
5 Jesus answered, Verily, verily, I say unto thee,
Except a man be born of water and of the Spirit, he can not enter into the kingdom of God.
6 That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
7 Marvel not that I said unto thee, Ye must be born again.