You have to run training exercises. You can’t truly know if you’re prepared unless disaster strikes, so what you want to do is simulate small, controlled disasters.
In a way this is like a vaccination against catastrophe. You build up an immunity by exposing yourself to smaller incidents.
In the days before GPS, my father used to take my sister and me out for “Sunday Drives,” where he’d let us essentially pick left/right/straight at every intersection for as long as we wanted, with the goal of getting us totally lost, just so he could test his ability to navigate us back home. Of course we weren’t in any real danger, so it was a perfect “stress test” for his ability to navigate more emergent circumstances.
If you commute to work, try getting there one day without your car – use public transportation, a bicycle, even Uber. Be familiar with the alternatives, their costs, their timing. Know those things so that if your car breaks down one day, you’re not panicked. Leave your cell phone at home and go a whole day without it, just to see what problems you run into – and build backups (like contact lists, etc.) so that if you ever drop your phone in a sewer grate you’re not hopelessly lost.
Give yourself small disasters. Prepare for the big ones.