Countdechickens:
I'm not actually a professional pilot, but I understand the basics of the problem you are going through, because I have a reasonable background in business; and subsequently an appreciation of the issues faced by people in similar situations to yours.
Somebody mentioned previously the comparison between your scenario and the sort of situation that professional sports people find themselves in; and also suggested that you try to get some advice from a pshychotherapist in that field. I would strongly agree with that view. If your employer has an occupational therapist on hand that you can talk to off record, go and see them as a starting point.
The same psychological 'trap' is faced by performers - actors, musicians, public speakers, etc.; and the solution is to change the way you visualise the situation. Common with the dreaded 'job interview' it is quite likely (and understandable) that you are preoccupying your mind with the "success/no success" element of the exercise. This stops you focussing on normal tasks and leads to panic/nerves. You need to break this train of thought and just concentrate on doing the job in hand. You need to program your mind to realise that you are not being assessed on your ability to determine whether your performance is good enough - because somebody else is doing that for you anyway. All that is required of you is to do 'your job' in the simulator, nothing more can be asked of you.
I know that may sound incredibly elimentary, or even illicit the 'easier said than done, mate' type of response, but there are some fairly simple mental exercises you can do to get over that phobia in a matter of weeks; and a professional in the field is the best place to get that advice.
Good Luck!