Maturity in God is when a man grows into completeness in Christ; the point at which he is fully flooded with God himself. At this level, a man has no need to be affirmed because he is in Christ Jesus.
The verse shows us that we are complete in him which is the head of all principalities and powers. This is the state of life that defines a mature christian; one who is complete, lacking nothing.
Some, for not knowing this they get married thinking marriage will complete them. Others find jobs thinking they will complete them; others even get intoxicated by substances seeking completeness and waste precious life because they didn't know that only God completes a man.
Settle it in your heart that God is the only source of completeness and until you find that God, you will remain empty and searching.
Prophetic Declarations
I thank you Lord for you have made me complete and surrounded me with your loving kindness. AMEN