Burnout happens when your training exceeds your body's and mind's ability to process the learning and you get diminishing results for your efforts. This can lead to spiritual fatigue and even physical injury. A few minutes ago in another thread, I wrote the following, "Everyone has their own timing and should flow with it." I think it applies here.
Varying your workouts as has been suggested may help. Delve into your art's history and philosophy and concepts and study the intellectual side of it. Cross training in a different activity may help also.
Your physical training, your body and your mind have to be on the same timing. If not, one or more of them have to be adjusted so they are in harmony. Sometimes cutting back on workouts by skipping a day, a week, or even years, can be a cure.
(In this last case, you may find yourself "playing around" with it every now and then. When you get tired of playing martial arts and feel like you're missing something, it's time to rededicate yourself, get serious, and jump back in. Chances are you will notice a general improvement in some areas over where you were before the layoff.)
Bottom line, (traditional) martial arts is a lifelong activity, so no need to push yourself to the point of burnout. Listen to your body and spirit. Old karate saying: "Even a plodding buffalo can walk a thousand miles." Steady effort will always get you to your destination.
