Forever Young, the stirring pop song from Alphaville, is a worthy exhortation.
"Forever young, I want to be forever young."
Be like little children.
The key word is "like".
Jesus does not exhort his followers to BE children.
He exhorts us to be full grown, growing in Grace and Knowledge of Him who loved us and died for us, to make us one with Him and receive all the fullness of His goodness. (cf 2 Peter 3:18)
"Now I say, That the heir, as long as he is a child, differeth nothing from a servant, though he be lord of all; But is under tutors and governors until the time appointed of the father. Even so we, when we were children, were in bondage under the elements of the world: But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law, To redeem them that were under the law, that we might receive the adoption of sons. And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father. Wherefore thou art no more a servant, but a son; and if a son, then an heir of God through Christ (Galatians 4:1-7 KJV)
We are Sons of the Living God by faith through Jesus Christ, yet that is not a call to act irresponsibly, in behavior and comportment no different that a slave in the household.
In fact, we are exhorted to grow in our walk with God throughout the New Testament Epistles:
"As a result, we are no longer to be children, tossed here and there by waves and carried about by every wind of doctrine, by the trickery of men, by craftiness in deceitful scheming; but speaking the truth in love, we are to grow up in all aspects into Him who is the head, even Christ, from whom the whole body, being fitted and held together by what every joint supplies, according to the proper working of each individual part, causes the growth of the body for the building up of itself in love." (Ephesians 4:14-16)
Paul's term for "children" — νήπιοι nēpioi — is very telling, a clear reference to a child who has not learned to speak yet, a child who babbles, who does not yet possess the power to use words.
Yet which words, or rather Word is Paul inferring? Why, the Word of God, "the truth in love", by which every believer may "grow up in all aspects into Him."
We grow by our knowledge of the Word of God, which is Truth (cf John 17:17)
If we in any way to resemble children, it should only be in our utter dependence on the Word of God in our lives:
" As newborn babes desire the sincere milk of the word that ye may grow thereby." (1 Peter 2:2 KJV)
The Word of God is our stable staple in a world of unstable, unreliable, and unholy sustenance. "It is written, That man shall not live by bread alone, but by every word of God." (Luke 4:4)