Chip my friend you are again right on the money, especially about not blaming yourself and keeping a cool head after this happens. It did for me a year ago and this client represented almost 30% of my income! You have to do a sincere and candid "post-mortem" after stuff like this happens but one never gets anything from doubting ourselves.
Keep going and find better and more creative ways to keep the pipeline full and don't try to oversell on your current clients.