A typical quant job interview is not unlike a Truth or Dare type of game: you either have to divulge every little detail of your educational and professional background ("Truth"), or have to answer some technical questions only a crazy mind can make up ("Dare"). Of course, unlike the game, you don’t get to choose which "activity" the interviewer will ask of you; indeed, the interviewer is likely going to ask you to do both Truth and Dare.
Why do I mention this? Likening the quant interview process to a game may help you better cope with the stress. Of course, if you absolutely need a job because, ugh, you have to eat and pay rent, nothing I say or anybody else says will help relieve your stress. But if you can somehow manage to have a positive attitude and look at the whole process as a game, and if you simply convince yourself to play the game fairly, who knows… your chances of success might be greatly enhanced. It’s like the Olympics athlete who focuses not on winning or beating everybody else, but instead focuses only on how to do his or her best. Such a mental state does not guarantee a gold medal, but from what many star athletes have told us, it does make taking the gold more likely.