When you are a specialist, even minute things might appear hugely problematic to you.
Remember the exams you gave in school/college, wherein you blanked out upon hearing the first question?
Remember your pupils dilating and your palms sweating profusely??
Don't let that happen to you again!
It is OKAY to not know the right answer.
Attempt it nonetheless.
Make a practice of it.
You'll be surprised at yourself!
Common sense will never ever fail you. :D
It is a proven fact.