Fast food was the worst job I've had, especially since I have anxiety and working in a big city.
People are rude, they don't care about your feelings, to them, I was just a young inexperienced worker that anyone can just come in - and take their frustration out on me, I'm not going to lie. Don't let it get to you, if you're in the front and show your emotions to the customer, they will take it wrong and might complain. I do'nt know if this helps, but I "devalued" working at fast food, that made me more relaxed coming in - I know that's weird.