Responses
You are right when it comes to children being able to feel negative emotions by using your logic, if I fake my happiness to say I'm alright to my child, they will still feel my negativity and if I deny it they will still know and still worry. Causing my depression to worsen because that will make me feel that I am doing something wrong.
Depression and trauma are not something that you can just bounce back from.

I understand Heesoo's emotions but as a parent he can't just push his baby away like that. He knows how horrible it feels to be abandoned by parents be he did the same to Byul. And though I'm sure Byul will be fine, small kids can feel the negative emotions their parents transmit and that rejection must have hurt.