How do I keep my cool during a full rush in the kitchen?

You can run your station on a normal night. Then the tickets pile up all at once, and the calm you had drains out. That is not a sign you cannot handle it. A full rush overwhelms almost everyone at first, because your mind tries to grab every order at once instead of the one in front of you. Speed in a rush does not come from moving faster. It comes from moving in order and not letting the pile in your head throw off the work of your hands. The best cooks in the storm look almost slow, because they are doing one thing fully, then the next, instead of ten things halfway. So when it hits, breathe once and drop your eyes to the single ticket in front of you. Fire it, finish it, move to the next. Trust the rhythm you already have on a calm night; it does not disappear in a rush, it just needs you to stop panicking and let it work. One plate at a time is how the whole night gets done.