Something I learned from listening to podcasts about comedy and stand up is to never tell the audience they are getting a bad show. If you think you are bombing and start trying to lampshade it you admit to the audience you don't have control over the situation and they start to have a bad time.

P.s. I was thinking of narcissists who will never be satisfied or seem to enjoy ruining events, not necessarily just being disappointed with something. Im sorry you feel that way sometimes