Smile It Can't Be That Bad
I hate feeling sad, but it is an emotion like any other and I as a person experience it from time to time like you do.
Sometimes I don't want to hear your words of condolence, your sad face, what I want is a reassuring smile.
There is evidence that Smiling actually makes you happier, even if its a fake smile. The simple action of pretending to smile actually seems to somewhat alter you mood towards a mood that would make you smile. Apparently others happiness can also be contagious, at least if your not a scrooge. If someone is very happy/cheerful, it tends to make us happy as well, and I have heard dogs abuse this heavily.
if that is true, then the opposite would also be true. To be sad, and to be confronted with the sad "I'm sorry" face is a double whammy, Your probably thinking sad things, feeling sad, and seeing sad faces, so it makes sense that it could be overwhelming.
It would then also make sense that putting up an apathetic act would help suppress emotion. Whatever "mask" you put on, your actual feelings seem to try and follow.