I think everyone who does anything creative goes through periods of being 'blocked'. Personally, I can't seem to do creative on a deadline (although many people do so, and successfully); I have to walk away from my problem project. Usually a trip to some good eye candy and connecting with other creative types helps me go back to my project with renewed enthusiasm; some of my tougher block periods require the successful completion of a small project before I can get back to the big one.
I know rotating projects won't be of much use to you since this one is a party invitation :wink: , but maybe thinking of it differently might help (like it being a party invitation and not a quilt on a deadline.) You mentioned that it will be on point - is it the setting triangles you're concerned about? Remember, there may be more than one way to accomplish a particular step :-)