Coop, I understand your frustration. It is very difficult to know how you stack up against the other candidates or prospective company standards without that feedback so, you have to work with what you know.
Critique yourself honestly and concentrate on all the areas you think you could have improved on. No-one has ever flown a perfect sim or sat a perfect interview. There is always room for improvement. Seek guidance from those you know that have been successful and leave no stone unturned in your preparation. Conduct mock interviews with your friends. Have them ask supplementary questions that you may not have anticipated. If you haven't done a lot of hand flying lately or you know you will be assessed on a particular sim, consider buying an hour for familiarity and to get your scan going.
Look like a professional. if your only suit is ill fitting or shabby then hire, borrow or buy one. Polish your shoes. Bind your resume, have copies for the people conducting the interview and know what is in it. Same with your log book.
If you are asked to bring copies of check and training records for the past 2 years then bring all of them from that time frame. Even if they are not particularly complimentary. I can tell you that candidates who have been just average in every other aspect have been given jobs because of how they responded to questions about those assessments. They owned them. Didn't try to blame any one else and were able to tell us what they learnt from that experience and how they are now better pilots.
From experience, a lot of people think they failed the interview when in fact they have failed the sim.
And don't believe just because you failed in your application for one airline, you will be undesirable to the next or unsuccessful in your next attempt. Back in the day, a lot of people who failed the Ansett selection criteria ended up successful with Australian or Qantas and vice versa.
Good Luck in your quest and don't give up. Nothing succeeds like perseverance.>
Chute, I can teach some one how to set up and fly an approach but i can't teach someone how to not be an a,hole.