Burnout is real. Overtraining is real. Sometimes you can get really into training and you train 5, 6, 7 days a week or two times a day and then you might wake up and feel like you hate training. You CAN burnout on training. You can't train hard every day all the time. Most sports have seasons. And with seasons comes the off season. Time when athletes can relax, do other things, work on specific weaknesses without the pressure of games or competition. Jiu Jitsu doesn't seem to have a real "season". There are some tournaments that are usually around the same time of year, each year...but there isn't really an "off season" to speak of. And training does not necessarily revolve around competition for a lot of people. So, how do you train hard and not burn out? If you train say, 3 times a week regularly and decide that you're so motivated that you want to increase your training, don't suddenly start training 7 times a week! Just add one day a week. Do this for a few weeks and give your body a chance to adjust. Then when that feels good, add another day, etc. If you suddenly jump up your training and your body isn't used to it, it will rebel. Then you'll probably have to take some time off. Try to make it a gradual change....for your mind and your body.
If you're already training a lot, like 6 days a week, it's good to take an extra day off every once in a while. Not only to catch up in other areas of your life (like going out on a date, spending time with your loved ones, etc.) but to also give your mind and body a chance to relax, rest and recover. An extra day of rest can do more good for your body and mind than your fear of missing one class because it might be the class where the teacher shows the "secret" move. But if that's the case (assuming that there is a secret move), maybe your teacher was just waiting for the day that you weren't there so he COULD show the move! LOL.