It is impossible to grow up unless you grow in the right soil!
Grow in grace and knowledge of the Lord!
"But grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ. To him be glory both now and for ever. Amen. (2 Peter 3:18)
Mark 4 demonstrates the importance of being soft, fertile ready to receive God's Word.
To grow up, we must grow in Him.
We do not have to strive to get into Him — by His death, by receiving His grace through faith, we become one with Him.
That was Christ's request in the Garden of Gethsemane:
"That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me." (John 17:21)
And this has been more than accomplished:
"And ye are Christ's; and Christ is God's." (1 Corinthians 3:23)
"If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God." (Colossians 3:1)
This truth Paul follows up with:
"For ye are dead, and your life is hid with Christ in God." (Colossians 3:3)
You are already in Him! And in Him, nourished by His Word, you can only grow up!