We do not want the "Christ in us" to remain immature, a baby. Just as Christ grew within Mary, so must He grow within us. Just as Christ grew "in wisdom and stature before God and man", we want Him to grow in wisdom and stature in us, but to do this, we must decrease so He can increase. As John the Baptist declared "He must increase but I must decrease". This is a truth of all ministry....if we wish for our "ministry" to grow in wisdom and stature before God (He always comes first) and man (inwardly, then outwardly), we must decrease, continually. Each time we give up more ground to Him, each time we die a little more to self - that portion of our soul that died can then be resurrected by Him, only now, in His image and likeness. Indeed, we cannot experience His resurrection life without experiencing our deaths. In this way "He that findeth his life shall lose it: and he that loseth his life for My sake shall find it". Paul said - "For me to live is Christ, and to die is gain" - Paraphrased - "In order for me to live (real life, eternal life) I need Christ, so the more I, that is self, that is my old man, die, the more I gain Christ".
The life we lose for His sake is the life the old man lives, where we hate Christ and all His ways, where we cling to our religion in His name but not to Him, where our old man dresses up real nice and sings songs to Him and gives Him money but doesn't know Him. No matter how much we dress up our old man in three piece suits and ties and cologne, he still stinks to God. The old man may look pious outwardly but he never changes inwardly - he cannot change. He's made his deal with the devil. He will secretly feed on fleshly lusts and desires which is why he must be crucified (lost) daily. If we lose him (the old man), we find him (the new man). By the way, once we've crucified the old man, it's possible to resurrect him, and if we've crucified our new man, we can resurrect him too. If you've crucified the wrong version of you, it's not too late to switch sides, to join the winning team. In Christ, we win by losing. We lose self, we gain Christ and we find self, we find ourselves, who we were always meant to be, not the false version of ourselves the world loves and embraces.
Feed your new man and starve your old man. "IF any man will come after Me, let him deny himself, and take up his cross, and follow Me". We cannot follow Christ unless we deny ourselves. Self and Christ don't mix. We will serve one and deny the other but we cannot serve both. Either the old man or Christ will live inside us. As we deny ourselves and follow Christ instead, we will find ourselves growing in wisdom and stature before God and man - Stature: The degree of development (maturity) attained i.e. the level of achievement. Paul, rightly so, complained of encountering too many Christian babies, able to drink milk only, unable to eat meat. Oh if Paul were alive and teaching today! He'd be shocked at all the babies who think they're mature Christians! He'd be appalled at the milk people believe is meat. "I have yet many things to say to you but you cannot bear them now". "Of whom we have many things to say, and hard to be uttered, seeing you are dull of hearing - for when for the time you ought to be teachers, you have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk and not of strong meat".
Again, the scriptures reiterate that everyone should be ministering to everyone, not just a few to the many. And again, we see a maturity problem. Folks, time and again I've asked Christians to name the foundational doctrines of Christ, the first principles of the oracles of God, and they cannot. I mean, in thirty years not a single Christian I've met can name them, much less understand and teach them, yet the writer of Hebrews calls them foundational, all other doctrines of Christ (not of devils or men) are built upon these six foundational doctrines found in Hebrews 6:1&2.