I'm annoyed that my fiance's grandpas funeral is today.
Is there a reason behind your feelings?
I wanted to go out with my friends.
The funeral is only going to happen once, you can always go hang out with your friends. You should respect the loved one and just attend the funeral.
I just hate gloomy get-togethers like this, you know?
Your annoyance is the least important thing right now. You need to support your girlfriend and attend the funeral with her.