For those who feel that they have a calling, I think it is helpful to recall the interaction between Moses and God. Moses was the king of excuses.
1. Exodus 3:11 Why choose me, I'm a nobody.
"And Moses said to God, Who am I that I should go unto Pharaoh, and that I should bring forth the children of Israel out of Egypt?
2. Exodus 3:13 I am not qualified.
"And Moses said to God, Behold, when I come to the children of Israel, and shall say to them, the God of your fathers has sent me to you, and they will say to me, what is his name? What shall I say to them?
3. Exodus 4:1 Since I'm a nobody and unqualified, why would anyone listen to me?
"And Moses answered and said, But behold, they will not believe me, nor hearken to my voice, for they will say, the Lord has not appeared to you."
4. Exodus 4:10 I simply don't want to do it, so send someone else.
"And Moses said to the Lord, O my Lord, I am not eloquent of speech, neither heretofore, nor since you have spoken to your servant, but I am slow of speech, and of a slow tongue. O my Lord, send, I pray thee, by the hand of him whom you will send."