After listing by name the priests who lived in Jerusalem (1 Chronicles 9:10–12), Ezra wrote, 

“and their brethren, heads of their fathers’ houses—one thousand seven hundred and sixty. They were very able men for the work of the service of the house of God” (1 Chronicles 9:10-13).

 
Were they very able men because God selected them, or did God select them because they were very able men? Why does it have to be “either…or”? God can and does both, making people able because He has selected them, and at other times selecting people because they had the ability. 
You are one way or the other, and which ever way you are, you can and should serve God, and He will bless you, and you will bless Him for having done so.