IF quotes are from Amy Carmichael, who was a Protestant Christian missionary that served in India for 55 years without furlough and wrote many books about the missionary work there.
Sometimes, when we are distressed by past failure and tormented by fear of failure in the future should we again set our faces toward Jerusalem, nothing helps so much as to give some familiar scripture time to enter into us and become part of our being. The words "grace for grace" have been a help to me since I read in a little book of Bishop Moule's something that opened their meaning. (Till then I had not understood them).
He says "for" means simply "instead": "grace instead of grace." "The image is of a perpetual succession of supply; a displacement ever going on; ceaseless changes of need and demand.
"The picture before us is as of a river. Stand on its banks, and contemplate the flow of waters. A minute passes, and another. Is it the same stream still? Yes. But is it the same water? No. The liquid mass that passed you a few seconds ago fills now another section of the channel; new water has displaced it, or if you please, replaced it; water instead of water. And so hour by hour, and year by year, and century by century, the process holds; one stream, other waters--living, not stagnant, because always in the great identity there is perpetual exchange. Grace takes the place of grace [and love takes the place of love]; ever new, ever old, ever the same, ever fresh and young, for hour by hour, for year by year, through Christ."