I’m so stressed about my drivers test how do I calm down?

Two shot of whiskey and a Valium should calm you down. Won't help you pass but you won't care anymore. 

Tell yourself you're ready. ...

Keep it a secret. ...

Don't skip meals. ...

Pretend it's a mock. ...

Arrive at the test centre in good time and make sure your diary is free. ...

Don't do too much on test day. ...

Stay off the caffeine. ...

Go to the lavatory.

Pretend a family member is in the car instead of the driving tester.

Have a nice wånk. Preferably not during the test itself...

By practicing even more, until there's no way you won't ace it.

Drive like a frightened old lady, looking both ways, coming to complete stops in plenty of time, seamlessly merging onto highways, and parallel parking like you were born to it.

The stakes for today's test aren't really that high in the big picture. Just a little embarrassment. Failing it doesn't mean you won't ever get a license, it just means you need more practice.