How can I prevent nerves from screwing up my driving tests?

Just failed test number 4. The situation's PERFECT for ping;I've had thousands of hours of practice and am now an extremely proficient driver,making nomistakes.The roads are easy here and the instructor even accompanies me,along with a very young policeman (this is in the Sultanate of Oman). But my problem every time is UNCONTROLLABLE BLIND PANIC that takes over and makes me jerky, inconsistent, and uncertain,as if I had a gun to my head. No matter how good and experienced I become, I make thousands of mistakes that I would NEVER normally make. My wife hasnt been out of the house more than twice in ten months, as its too hot to go outside here without a car, and my 2 yr old daughter too. I have to find a way to overcome my neurosis and get ped on my test.Any suggestions?