By saying this Paul intimates that even his assurance and pride are to be given to the Lord, because it is by his favor that he has them. Someone who has confidence in the power of the gospel has confidence in the God who enables it. Thus God is glorified by all godly work. A person who has not received power from God cannot glory in the Lord, because he is seeking his own glory.
Keep thyself pure as the habitation of God. Thou art the temple of Christ. Thou art the instrument of the Spirit. Thou knowest in what way I have brought thee up. Though I am the least of men, do thou seek to follow me, be thou an imitator of my conduct. I do not glory in the world, but in the Lord. I exhort Hero, my son; "but let him that glorieth, glory in the Lord." May I have joy of thee, my dear son, whose guardian may He be who is the only unbegotten God, and the Lord Jesus Christ! Do not believe all persons, do not place confidence in all; nor let any man get the better of thee by flattery. For many are the ministers of Satan; and "he that is hasty to believe is light of heart."
[AD 384] Ambrosiaster on 2 Corinthians 10:17