I own some fast food restaurants and, for a short time, managed them directly, hands-on. During rushes, especially when shorthanded, you feel you are being crushed by disappointed customers filing in the door, and there's nothing you can do to make things better at that moment. When I realized that, I also found my answer. I can't make things better so I will only concentrate on what is in front of me and do the best I can; and the rush will end soon.
Everything I do, I do with personal pride, so when things go bad, it hits home. I also realized that most things aren't running as bad as you think they are cause you know how things are supposed to work but your customer only sees the result of your efforts.
When doing rote things under pressure, it helps to hum random notes.