I have this problem come out in dinner/dinner parties too- I just don't want to cede to conventions and often my reaction sequence is as follows: - say "no" to every invite, especially in person. - Ways to say no on stage that get more absurd. Dmitry martin example of saying I ahve diarrhoea as a way of saying no. - Thining about who is invitie: white coworker, housemate, etc. - then I will get asked a question about why I won't just say "yes".