I was listening to a few excerpts from sermons by Alistair Begg and found one very comical. Holly was listening with me and made the comment, "Is he talking about you or Timothy?" He was making the point that Timothy would have been the last man most search committees would choose because he did not fit the contemporary "mold" of a pastor or preacher. Timothy was young, shy, and had stomach problems.
I'm young, not the best in crowds, and have had my share of stomach problems. But, like Timothy, God chooses the weak and foolish things of the world to show His strength and His wisdom. Don't be anyone but who God made you to be. To be sure, work on your weaknesses and strive to improve in those areas for the glory of God.
However, don't look at what some would call "weaknesses" without remembering that God made you with those personality traits or physical limitations and did so for the purpose of exalting His strength, power, and wisdom through your life for the glory of His name.
You can watch/listen to the whole excerpt below.
There are also two other excellent words of counsel concerning preachers/pastors, preaching, and the sufficiency of the Word of God here and here.