He must increase, but I must decrease. (John 3:30)
The Bible describes the call of God as the high calling (Phlp. 3:14). Yet the higher your calling takes you the lower you must become in our own eyes, which basically means we take all the accolades that come our way and passing them on to our Almighty God. Our Lord Jesus Christ said of John the Baptist, There is not a greater prophet (Luke 7:28).
Yet John said of our Lord Jesus Christ, He must increase, but I must decrease. When God called Ezekiel into the ministry, Ezekiel felt so inadequate that he fell on his face in front of our Almighty God and He said, Stand up on your feet, and I will speak to you (Ezek. 2:1). Now, how's that for humility?
We don't know exactly what the thorn in Paul's life was, but we know why he had it when he said, Lest I should be exalted there was given to me a thorn in the flesh (2 Corinthians 12:7).
Thorns come in many forms. God customises them to our individual need. Our thorn may be a problem child, or a turbulent marriage, or a stubborn habit, or a lifelong affliction. It's what deflates you when others try to exalt you or try to put you down. It's what enables you to receive a compliment and not become arrogant.
Paul says, Not that we are adequate in ourselves to consider anything as coming from ourselves, but our adequacy is from God (2 Cor 3:5 NAS).
If we are to demonstrate God's Kingdom on earth, then it will only happen through His assistance. That's why He allows our feelings of inadequacy. Its our neediness that forces us to rely on God for strength. Thats a difficult concept for our ego to accept! But when we do, we become effective in His service.