What is spiritual growth? What is spiritual maturity? What is it to go on in the Lord? I fear we have got mixed ideas about this. Many think that spiritual maturity is a more comprehensive knowledge of Christian doctrine, a larger grasp of scriptural truth, a wider expanse of the knowledge of the things of God; and many such features are recorded as marks of growth, development, and spiritual maturity. Beloved, it is nothing of the kind.
The hallmark of true spiritual development and maturity is this: that we have grown so much less and the Lord Jesus has grown so much more. The mature soul is one who is small in his or her own eyes, but in whose eyes the Lord Jesus is great. That is growth. We may know a very great deal, have a wonderful grasp of doctrine, of teaching, of truth, even of the Scriptures, and yet be spiritually very small, very immature, very childish. (There is all the difference between being childish and child-like.) Real spiritual growth is just this: I decrease, He increases. It is the Lord Jesus becoming more. You can test spiritual growth by that.
By T. Austin-Sparks from: The Cross and the Way of Life – Chapter 4