Wedding invitation accepted but now I can't go

Dear Limo Princess,
Have responded yes to wedding and as it getting closer to the date, we are unable to make it. what do I do?

Dear Peggy,
You should call the bride to be and tell her that you are terribly sorry but you will be unable to attend the wedding even though you though had previously accepted the invitation. Apologize profusely and tell her that you very much wanted to share her joy but that a situation has arisen that is both critical and beyond your control and that you hope she will forgive you for canceling at the last moment. You should also send a small gift even though you aren't attending the wedding since she will have to pay the caterer for your dinners whether you attend or not. It is considered extremely rude to cancel an invitation to a wedding that you have already accepted for all but the direst emergency. No reason to cancel an accepted invitation to go to a different social engagement in place of the invitation you previously accepted will do except the following:"We regret that we are unable to attend your wedding as we have been invited by the President of the United States to dinner at the White House".