How do I stop my coworkers from getting bitchy and get on the same page?

We are short staffed at the moment and people are getting pissed off over any and every little thing. I work in a restaurant. I'm trying to get everyone to be on board and be a team player like me. But everyone is getting pissed over almost the least little stuff. It used to not be this way. How do I get them to calm down and try to play as a team?
How do I stop my coworkers from getting bitchy and get on the same page?
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