I'm not very good with criticism myself, and I'm sure working with the public like you do would be hard for me. However, here, I hope, are some thoughts that might help. 1) These people don't know you personally. 2) They are hungry and so are likely more irritable and harder to please as a result. 3) They like their food a certain way. It might be weird, but that's them. 4) Sometimes they might gripe about something that's not your fault. You are a convenient scapegoat. If it wasn't your fault, then you might want to mentally fuss at whoever really deserved it. 5) Learn from mistakes that are your fault. Sometimes people actually are trying to help when they point out things we can do better. 6) You do have a job, and people might think working at a fast-food place is not good, but it's better than no job and you ARE doing people a service. I really should thank folks like you more often, because I know it's hard to do and I'm glad you're doing it.