Professional flying involves a never-ending serirs of checks, failure at which has the potential to bring your career to an end. You have to face this situation 3 or 4 times a year - medicals, line checks and simulator checks. And that's once you are qualified and type-rated; while you are in training you are constantly being assessed and, if you are sponsored or in an airline-associated training scheme, at risk of being chopped.
This is stressful. Many people find they can't cope with the stress, but most do cope one way or another. You never get used to it though! You have to give yourself a chance, but it's no disgrace if you feel unable to countenance this level of examination for the rest of your professional life - no other profession suffers anything like it.
Scroggs