Our service to God is from the spirit, the inner man. The value of our service and sacrifice is not in the time we spend, or the strength we expend, but in the surrender of our hearts to God as we serve. We cannot serve God without total surrender of our person to God – for then our service would be unacceptable to Him. The strength for acceptable spiritual service comes from the One we serve, and that strength is only released into our weakness and inadequacy.
The point of what I am saying is this: we cannot take pride in our service to God (and humanity, by extension) because God is the giver of all grace and every good thing. Our service must begin from a point of admission of our insufficiency and inability, even if we seem sufficient and capable. It is crucial to acknowledge the supremacy, ownership, and authorship of God in all we are, and all we have. It is only from that point of acknowledging our emptiness without Christ that we can truly offer acceptable service and sacrifices to our God and Father.