The verse highlights that only Jesus has ascended to heaven and returned, and only through faith in Him can we attain eternal life. We are reminded in this verse of the importance of placing our faith in Jesus as the only means to reach heaven. It also emphasizes the fact that Jesus is unique because He came from heaven and returned to heaven, and He is the only way to ascend into the spiritual realm. 
The Lord Jesus explained to Nicodemus step by step the importance of a new spiritual birth. Even though Nicodemus understood the words written in scripture, he was unaware of the truth. A full revelation of this truth was made by Jesus, the only begotten Son of the Father. The letter of the law was well known to Nicodemus, but he was not yet aware of the Word of truth, the Word of life, the Word of light, and the Word of salvation that Scripture mentions.
Truthfully, it is only through a spiritual rebirth, given by God, that one can be freed from spiritual ignorance and gain acceptance into God's kingdom. Jesus Christ, the Son of Man, has been appointed by God as the heir of everything and the only one who has ascended into heaven to bring about this rebirth.

Dear Heavenly Father, I thank You for sending Your only begotten Son, Jesus, to reveal the truth about eternal life. I acknowledge that nobody except the Son of Man has ever ascended to heaven except for Jesus Christ. I firmly believe that through my faith in Jesus, I, too, can ascend to the spiritual realm and attain eternal life. I pray that You help me to understand the truth that flows throughout the pages of Scripture and to put my trust in Jesus as the only way to reach heaven. 
In Jesus's name I pray. Amen.