Everyone has experienced burn out at one time or another during their martial arts training.  I have experienced and dealt with burn out quite a few times in my experience as a martial artist.  So what can you do to deal with burn out? 
Take a break from it for a while.  Take one or two weeks off, or as long as you need to give yourself enough time to recuperate.  Doing this will not only give your body and mind time to rest, it will make them stronger.  However, during that duration, you should not just sit around and do nothing.  This is counter productive.  Instead, you should find another hobby or training regimen that will help you during your off season. Take up bouldering or rock climbing if you are adventurous.  You could also start running or cycling to keep your cardio up.  The sky’s the limit on what you can do to supplement your training.