IMHO, the ability of reflecting on one own's performance, objectively, is key to becoming a proficient pilot. It will certainly also help with passing interview sim checks. Not few out there have an attitude which you do not want to have on the flight deck. Those individuals are attempted to be singled out in selections. People believing they were great whereas their performance was clearly below standard are dangerous.
Being over critical with your own performance is a good thing. It will most likely never let you become satisfied and help you keep motivating yourself to constantly improve.
That said, when I hear pilots talk about their own perfect performance of some sort I get suspicious. I'm not the best out there but not the worst either. Still, a perfect flight of mine I find is yet to come.
Failing a sim is not the end of the world. This has occurred to many of us. On the day, a lot can go wrong, but a lot has to go right.
I myself have had two jet interview sim checks. I failed both of them. I wanted to cry after each. I also had two interview sim rides for TP and passed them both. Also, I had two flying interviews for piston jobs which I also passed. Having over 1,000 hrs more in my logbook this time around I know I would pass those jet sim checks today.
At some point in your career all will fall into place.
Don't be too hard on yourself but figure out where you did go wrong and correct for it.