Preparing for the unknown can be pretty daunting when you're completely out of your element. Scott Belsky, founder and CEO of Behance, suggests that the key is to imagine yourself in the shoes of someone else who regularly deals with your particular situation.
Obviously you can't be an expert by way of imagination - it's just too much effort for a temporary issue. But if you want to avoid getting flustered, you want to look at how an expert would handle your situation and see if there's a way you can adapt their approach to your circumstances. Even if you don't come up with anything all that great, you end up psychologically normalising your inflated concerns so you're not thrown for a loop when something unexpected happens. Basically, just the act of thinking about the problem and how an expert could handle it will help you feel more comfortable if it arises and you have to deal with it.
How to Navigate the Unexpected and Keep Your Cool [Open Forum]