I get stressed and stuff, but sometimes I just relax.
I just realize that what happens, happens, that my actions at a certain point in time are irrelevant to the final outcome, stressing will just make it worse so just relax, have fun and just take it like a stride. It's how I do exams.
The other thing I do is plan constantly, always have a nice flexible plan in place and when something goes bad, I reformat the plan and find ways to deal with it