Psalm 123:2 As the eyes of slaves look to the hand of their master, as the eyes of a female slave look to the hand of her mistress, so our eyes look to the Lord our God, till he shows us his mercy.
In any position of work or service, you depend on your boss to ensure you can continue to do your work as effectively as possible.
When God calls us into service, we should be willing to obey and trust Him to make sure we can continue to work effectively for Him!
God will ensure you are able to do what He asks because He alone knows what you are capable of given the right circumstances.