There is nothing that we have that hasn't been given to us. What we give back is what God had already provided.
But why should you [give back]? You're already 'saved,' and God is driving
Why not. He gave us everything. Can't we give back a little?
Of course. But, playing Reformed advocate, we could say God doesn't need it, does He? Why engage in idle and repetitive tasks and useless rituals such as praying, offering gifts to God he doesn't need, or going to church, when they cannot change what has been predestined?
He determined from all eternity who will have what, so there is no point in asking, praying, and going to church. You are either the (s)elect or the reprobate. It's decided, it's done. Everybody already has a ticket to heaven or hell. So, sit back and just do whatever your heart desires, and let God do the driving. In fact, why even bother with God?
And, let's not make a mistake of calling this a "fellowship" with God. We are not his "fellows," HD. According to the Reformed theology, we are His peons; we play no role other than where the puppet master puts us. So, we might as well rename the whole relationship to Puppet Master and His Puppets church.
You know, Protestants amaze me as much as solipsists do. There is actually a great deal in common between them. Next time you get sick, please don't seek medical help. After all, whether you do or don't, God has already determined if you will stay or leave. And since you know you are already saved, why in the world would you wish to stay?