I learned not travel with just one credit card after my CU botched a software update while I was in a middle of the trip in Prague - already checked out from the hotel but not yet taken the rental car to drive to the next hotel in a different city. The looming possibility of sleeping in the street was rather instructive.

Since then I always carry three credit cards when traveling, from three different banks, and each from a different payment system in case if a systemic issue.