Tim 1:12  "I give thanks to Christ Jesus our Lord who has strengthened me, because He considered me faithful, appointing me to the ministry--"  Once again Paul wants to be sure that everyone knows that God appointed him.  And one other thing…I have always believed that the first prerequisite to a happy life is a thankful heart.  Paul was thankful that Christ had chosen him, and he gave all the glory to Christ his Lord.

Preliminary Hellos, a discussion on why he had left Timothy behind, a description of the lawless and the kinds of sin they are involved in, a number of affirmations of God's having chosen Paul and then, lest we think Paul is bragging about his apostleship, Paul begins to confess.  He begins to describe himself.  And it isn't pretty.

Paul tells them about the despicable man that he was when Christ saved him.  He tells us in this letter to Timothy (which he knew everyone at Ephesus would hear about or read) exactly what he had been before he met Christ:

I Tim. 1:13a  "One who was formerly a blasphemer, a persecutor, and an arrogant man: but I obtained mercy..."  He certainly wasn't bragging about being appointed to the ministry. Quite the opposite, he wanted everyone to know the extent of his sins.   He was making his confession to Timothy and to the church at Ephesus that he was undeserving, but that Christ was merciful.

James 5:16  "Confess your faults one to another, and pray one for another, that you may be healed. The effectual fervent prayer of a righteous man avails much."

In I John 1:9 we find that "If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness,"  Paul was no longer arrogant, he was humble.