Years ago I went on a hike through the Italian Alps with two local women. One had brought a devotional book, and during our break, as we sat and munched on sandwiches and enjoyed the landscape, she read out of it. It was one of Watchman Nee's works (I don't remember the title). He was saying that as Christians we have the tendency to pray that God will increase our virtues -- humility, chastity, faith, etc. -- whereas the core of Christianity lies in the recognition that it is Christ who is to be all in all.
On a practical level this would mean that instead of praying, "Lord, increase my faith", I can pray, "Lord, I thank you that you are all the faith that I need."
This offended me. I very much viewed the Christian life as a transaction, an example of lived-out reciprocity. God does something for me, I do something in return. There is no doubt that what He will do will always be much more momentuous, but that's because He's God. I certainly shouldn't come to Him expecting Him to do for me what I could be doing for myself.
And faith -- virtue in general -- I considered something that I should be able to achieve, with a bit of willpower. Sure I would say that I needed God's help in this. But it struck me as ungrateful to try to make God "do all the work." It sounded exactly like the sort of fluffy talk that people use to try to worm their way out of the austere difficulties of attaining virtue.
Grace always offends these religious sentiments of ours. The fact is that when Jesus offers to "do all the work", it isn't just a polite offer. It isn't like someone saying, "can I help you?" to someone who could also handle it alone, or who maybe needs a hand. Jesus in fact has done all the work, and the best way for me to both glorify him and, as it were, "return the favor", is to not try to do it again.
I had thought of the essence of Christianity as being, "you died for me, and in gratitude I'll try to live a virtuous life."
It took me many years to understand that my own virtue, and my attempts to increase it, were a larger obstacle between me and God than even my sins were. I think I did not understand the essence of Christianity until I was able to pray, "you died for me, and in gratitude I'll surrender my attempts to live a virtuous life."
Because a virtuous life turns out to be something we can only achieve by surrendering our efforts to achieve it to the One who has achieved it. If I could get there myself, I would not need Jesus. Glory be to Him! By being the faith I need, He counts Himself to be the faith He requires me to have.