Mercy has a serenity of spirit which enables her to accept life's unfairnesses without complaint. When Kit asks her how she can bear "always staying behind" because of her physical handicap, Mercy replies,
"Oh, I settled that a long time ago. I remember it very well. Father had carried me to the doorstep, and I sat there watching the children playing a game in the road. I thought of all the things I would never ba able to do. And then I thought about the things that I could do. Since then I've just never thought much about it" (Chapter 11).
Mercy has chosen to focus on the positive things in life, and to be thankful for the things she has. She is "the heart of the Wood family", and, in her patience and kindness, an example of "the Puritan feminine ideal" (Enotes).