It may seem like the end of the world but it is not. There will be another opportunity. Keep your head up and forge on. The rejected take off is one thing on a check ride I always made obvious when giving a check because there was a lot of room for error. I have seen people fly a perfect checkride and almost fail because of a rejected takeoff. The advice about over preparing is good advice. The bigger issue is to talk to a counselor about test anxiety. It is real and is something not addressed in the aviation profession. I always try to make an applicant feel at ease when giving a check because I realize that it is a stress full event. One thing to remember when getting checked is that you know what events are required to be checked and keep that in mind. There is a danger of over anticipating and making things worse but it is all about test strategy which will help with the nerves. In any other profession there are retest with out any penalty that will follow you. Take a few days and try to relax. Get another flying job and eventually get in to the training department. When asked to explain in an interview tell them you learned to address the issue by helping train others.Good luck and remember your human and just because this happened to you does not make you any less of a good person.