The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair.
“I never expected any sort of success with 'Mockingbird'... I sort of hoped someone would like it enough to give me encouragement.”
“Our assistance in Somalia has been remarkably effective and successful, and we have helped with very small resources - a large group of people and we can now do even more.”