It won't be too challenging. I mean, you WILL get nasty customers sometimes and you WILL make mistakes, but it's ok. Do your best to pay attention to the orders, recite them back, and you will probably be fine.

Once, at a Taco Bell, I asked for a chicken burrito and a bean burrito. You know what the person who was clearly not paying attention gave me? A taco and a bowl filled with potatoes and cheese. I was irritated because I took it home and saw how badly the order was messed up. I should have checked, but I figured it was an easy order. I talked to the manager and all they did was put my name down for a couple of burritos. The point is, that was an employee screw up and the worst that happened was Taco Bell lost about $3.50. And I still go to the same Taco Bell. Very low stakes. Do your best, keep your chin up, and know that even a stupid mistake is still pretty low stakes.