We mature in many ways—physically, intellectually, emotionally, and volitionally. But of paramount importance is our spiritual maturation.
Spiritual maturity is the development of Christlike character and behavior. In a word, it is holiness. It is God’s primary desire for those of us who are His children, and He has provided us with everything we need to experience it—“His divine power has granted to us everything pertaining to life and godliness” (2 Peter 1:3). And maturing in Christ-likeness should be the aim of every true Christian:
[U]ntil we all attain to the unity of the faith, and of the knowledge of the Son of God, to a mature man, to the measure of the stature which belongs to the fullness of Christ. 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 [e]speaking the truth in love, we are to grow up in all aspects into Him who is the head, even Christ....(Ephesians 4:13-15).
So, as those who have been chosen of God, holy and beloved, put on a heart of compassion, kindness, humility, gentleness and patience. (Colossians 3:12).
Therefore as you have received Christ Jesus the Lord, so walk in Him, having been firmly rooted and now being built up in Him and established in your faith, just as you were instructed, and overflowing with gratitude (Colossians 2:6-7).