If all else fails, just breathe. Sometimes realizing that you are becoming stressed out can help you calm yourself before you lose your temper or act in a negative manner. Training yourself to count to ten really can help. If possible, take a brief break to regroup. If you can't move away from your station, mentally think calm and focus on self control.
Self discipline is a valuable asset to have in a fast food working environment.
There will be times when everyone is taxed and rushing about, especially during peak hours like lunch time. This is when the stress is most likely to feel overwhelming. These are also the most important times in which to strive to keep your cool and focus on your duties. Prepare yourself mentally by planning to face even the most stressful times with a level head. Your efforts will be rewarded in that your job will be much easier and you will be more likely to be noticed for your productivity.