You can't always buy what you want when you want it
France shuts down Sundays, Mondays, and sometimes Wednesdays. Try buying groceries during lunch hours and the locals will laugh at you. When the market is closed, it is most likely going to stay that way for some time. The easiest way to get over not being able to buy what you want when you want it is to take a coffee break, as the French do. Keep a book on you at all times and use any "fermé" sign as an excuse to catch up on some reading.