Quote about C.S. Lewis from J Austen Book

"C.S. Lewis said every time you make a decision, you change the central part of you that chooses. He meant moral choices--whenever you choose to lie, for example, or not to lie, you change the substance of who you are and what you are likely to do the next time you have a choice to make."
(from A Walk with Jane Austen by Lori Smith)

She says the quote is in Mere Christianity. It reminds me of Charlotte Mason's perception of habit, how it changes the substance of the brain.