In a scene that draws on Doc and Codi's shared medical experience, Doc makes the point that the human heart is the wrong organ to symbolize the fragile human ego. The heart is tough. It's easy to sew up it if there's a violent injury. His preferred symbolic organ would be the liver, and Codi says she knows just what he means:
Once in ER I saw a woman who'd been stabbed everywhere, most severely in the liver. It's an organ with the consistency of layer upon layer of wet Kleenex. Every attempt at repair just opens new holes that tear and bleed. You try to close the wound with fresh wounds, and you try and you try and you don't give up until there's nothing left. (21.84)
Closing the wound with fresh wounds is basically what Doc and Codi have tried to do in coming to Grace. It seems to be going better for them than it did for that poor lady in the ER.