Like Meez said it isnt life and death , and i usually remember service will always end....EVENTUALLY
The problem with my kitchen as that we are friends inside and outside of work , so we usually try to specify to never take what happens in the kitchen seriously ( since line cooks during a rush can act like a-holes).
Now the stress of doing in event is far worse , because something can and will always go wrong , either inside or outside of the kitchen , i usually try to remain calm all through out service , and stay focused. If we are in the sh** , then thats when i stop talking and start doing the harlem shuffle.
Remember its just a kitchen , your dealing with flames , tools , equipment , eletricity , co-workers , food etc.... anything can happen , your job is to cook , produce , clean up and go home , the rocks in the middle of the road you either drive over or around them , they get in your way but dont stop you.
Also a few good screams in the bathroom or the cooler usually help. Or even swearing out loud , as long as it isnt directed towards co-workers.
This is why i find having a hobby or something to do outside of work a good way to destress.