The title, it should be disclaimed, is not what the astronauts or flight controllers believed. It's a poor abbreviation of the following:
"No, when bad things happened, we just calmly laid out all the options, and failure was not one of them. We never panicked, and we never gave up on finding a solution."
source: https://en.wikipedia.org/wiki/Gene_Kranz#.22Failure_is_not_a...