The prime rule, which supersedes all others, is to not have shit go wrong. That's more important than following any of the other rules; if you follow all the other rules, the rules which you think are important because they're written down, but miss on the prime rule, then your ass is in trouble. Even if it doesn't end your career, it will still hurt it.

When things really matter the foremost objective is never "follow the rules so your ass is covered", it's to not have a situation where that ass covering is relevant in the first place. Outcomes matter more than preforming according to the book.