Have you ever been driven to do something for God not because you felt that it was useful or your duty to do so, or that there was anything in it for you, but simply because you love Him? Have you ever realized that you can give things to God that are of value to Him?
There are times when it seems as if God watches to see if we will give Him even small gifts of surrender, just to show how genuine our love is for Him. To be surrendered to God is of more value than our personal holiness. Concern over our personal holiness causes us to focus our eyes on ourselves, and we become overly concerned about the way we walk and talk and look, out of fear of offending God. "...but perfect love casts out fear..." (I John 4:18)
We should quit asking ourselves, "Am I of any use?" and accept the truth that we really are not of much use to Him. The issue is never of being of use, but of being of value to God Himself. Once we are totally surrendered to God, He will work through us all the time.