[Demiurge]

They're inaccurate, but they're fundamentally fate altering when you can put some pieces of information together to generate a non-obvious conclusion that prevents a huge disaster. Good planning is not about assuming something works, that's where most of the time the plan is wrong, it is to assume something doesn't work, and what can be done to forge ahead in such a case. Good planning is also revising plans any time new information is learned.