The faster you can accept that everything has changed, the better off you’ll be during the apocalypse

No plan of operations extends with certainty beyond the first encounter with the enemy’s main strength.” 

Or, as Mike Tyson said, “Everyone has a plan until they get punched in the face.”

You have to find a way to survive that adjustment period of shock and help others get through it. You have to find a way to limit denial. The place to start is with the opposite of denial: acceptance. If you have the imagination to accept that aliens are invading or that the dead are walking, then you’ll have the imagination to accept that this earthquake is indeed the Big One. The more you can accept that things have changed, the less time you’ll waste on denial and “milling” (disaster-speak for checking in with other people and doing nothing) and the sooner you will take action. If the shit really hits the fan, I’ll take a semi-decent plan right now over a good plan in ten minutes or a perfect plan later. The faster you can accept that everything has changed, that everything you’ve worked for all your life is now gone, the better off you’ll be during the apocalypse. I’m not talking about actually redefining reality; I’m talking about adopting an attitude—“What’s right in front of me?” It’s about looking at what you see without preconceptions. If you start limiting your emergency plans to only what you think is likely, then you’re screwed.

The Disaster Diaries: How I Learned to Stop Worrying and Love the Apocalypse by Sam Sheridan