Too late for quick [story of my life] - but for what it is worth:
In such situations, I have learned over time, the more I anticipate the more I panic, the more I plan, the more I freeze. Where I go is my basic advice given to students coming up for a big exam:
No all night study > no prescripting. Get a good night's sleep > do things in the time leasding up to the appointment that will calm and relax. In the exam do not fixate on one question > just let go and let it happen.
Nothing is infallible - but if you are doing a paracvhute jump you to noty brace your legs. Limp down. Trust. Detach.