It's hard because we all 'see' happiness and joy around us. The commercials scream happiness and buy, buy, buy.... but for a lot of us it's a facade.... the holidays are really hard on many... especially the first ones after a betrayal.
I still struggle at 4 years with Christmas... major triggers to get through.... and now until the next horrible holiday of Valentine's Day will be rough... I had found out what he was doing in Dec. and he continued until I couldn't take it anymore in Feb. That's when his denial was soooo obvious and the shit hit the fan. Since then those two holidays have been especially hard. I mostly try to just ignore they exist but it's soo hard with all the crappy commercials and fake happiness everyone is having.
Since all this has happened to me I find I am a more emotional person.... when something is happening to others I care about or even watching the tv or a movie I feel a punch in the gut sometimes and thrown for a serious loop and need to reset my bearings. I don't think this is uncommon. What you will realize is that the time period to heal is different for all of us and that some of us have been hurt more than once... I think that makes it harder to recover from.
Just keep muddling through like the rest of us.... it's all you can do for now.