Always remember: what doesn't kill you makes you stronger. Don't give up on something that keeps you disciplined and remind yourself why you were going for that rank in the first place. I would recommend you read a book entitled The Fighters Mind: Inside the Mental Game by Sam Sheridan. I recently finished it and it was a special book, let me tell you. It completely changed the way I look at fighting and gave me a new reason to keep at it.
P.S. a black belt in what?