To serve is different than to give. When an article is owned by the receiver, it is served. When an article is owned by the server, it is a gift.
Serve God, as a purpose is to render to God that which He already holds title.
Two quick reminders about service from Jesus, tell us: You cannot serve two masters; and whatever we do for His children we do for Him.
Sound simple doesn't it? It should be simple that when we serve His children, we are serving Him. But, there are many who want to confuse serving God with giving to God.
Here is proof of ownership: whatever He created is His and He created all.
So logic tells us we cannot give God anything because it is already His. On the other hand, what He gives to us, we can return to Him. Of course we can give to other children of God the gifts we have received, and in doing so we then serve God.
Christ underlines the importance of service to God when e says we can't serve two masters.
In this way we understnd that God alone is our Master, and it is He alone that we serve through Love and Knowledge, both of which are given to us from God.
Further, we can begin to grasp the to serve God is an act of our own free will that we can completely understand.
And that is how we stay on target; that is how we fulfill our purpose; that is how we can know, love, and serve God.
At the same time, it is good because we can humble ourselves by realizing He is the giver and we are the servers.
And we deny those who would have us believe we own anything that God created because there is only one God. Begone Satan, in the name of the Father, and the Son, and the Holy Spirit. Amen.