And truthfully... the response when God reaveals what He wants to do in my life goes from 'yeah! Bring it On' to 'Oh cripes, what have I gotten myself into' when we really get our hands dirty into it.
We face fears.
David had to face Goliath
Moses had the fear of public speaking
Noah was asked to built an ark and he probably had no idea what it is.
The ten spies had fear when they saw giants in the land.
Bottom line is that God has never asked us to do anything that was easy, if it was then we wouldn't need Him and we must fight through Fear :) Perfect love drives out fear, I believe David had a love and passion for God and his people that he didn't had the fear to face Goliath.
If God has called you, He will equipped, sustain and empower you. Of course it might seem impossible but what is impossible with man is possible with God, that's why in Zech 4:6 it says its by God's spirit, not by our might or power. You may think you are a nobody, or an ordinary person who God wouldn't use. Think again~! God is in the business of using ordinary people to do extraordinary things!!
Acts 4:13
The members of the council were amazed when they saw the boldness of Peter and John, for they coyld see that they were ordinary men with no special training in the Scriptures. They also recognized them as men who had been with Jesus.
Be blessed =)