I'm mad at my boyfriend for partying while I'm mourning.
Why does his partying upset you?
I'm upset because his behavior is not sensitive to my situation.
It does sound like he's not being very sympathetic to your feelings. If he's not helping you feel better while you're mourning a loss maybe you should take some time away from him.
Yeah, his celebration is upsetting.
Yeah, you shouldn't celebrate what your SO mourns.