..to see one's WS singing and dancing around the house, while the BS is suffering in the depths of dispair is a tough thing to watch.. and on the surface, it seems quite obvious why the BS would be taken aback and think.." is my WS so oblivious to my sad state of mind???"
..but in reality, i believe it is their desperate attempt to normalize and push away all the negative feelings. It may be an attempt to push down their feelings of guilt/shame and "put on a happy face" trying to draw out the BS into a better frame of mind.
I agree that it would be appropriate for the WS to acknowledge the BS's feelings of sadness in that moment, 'I'm so sorry, but can we try to be happy together?" It seems totally understandable that the WS would initiate an outward attempt to not dwell in the sadness..but instead, try to promote some brighter outlook to the future.
It does present a very mixed bag of emotions for both people. I think the key is to realize that the BS is not always able to jump right in with the laughter and merriment. Often, the BS sees nothing to be merry about! ..and may see their WS's jovial behaviour as insensitive and uncaring .. like they are over it and are unaffected by the devastation the BS is experiencing..
The WS may be feeling like crap inside but may not want to add to the depressed state by the outward behaviour of doom and gloom.
The strategy is to put on a happy face and hope the BS will follow suit.