I've been teaching Body Pump 3x a week for about 3 months. For those that aren't familiar, it's the "Original Barbell" class. It's about an hour long and each song focuses on lifting a different body part. Since I've been teaching this class I've lost the motivation to then go back into the gym and lift more... I don't really enjoy the class, it's easy to do, and while I'm supposed to be connecting with my participants I feel like I'm staring off into space. I don't get paid a ton, and then I also have to take the time to drive to get to that gym, when it's not the one I would normally go to anymore (it is my old gym that I spent a LOT of time at). I have lost a lot of my strength that I had been working for, and it just doesn't make me happy. My participants love me, and often my class is packed... I don't know if I should just wait it out and maybe I'll like it more when it's not as new to me and comes easier, but I'm thinking it's just a waste of time.
I think I'm just selfish.
That is why they say that don't make your hobby as your occupation, because then you would have neither. I am joking; I don't agree with it.
There are ways to make your job more challenging. May be you can make your lessons to be more interactive; more actively involve your students in your lessons. You can also take more personal interest in your students (like asking them about their individual fitness goals, etc). May be you can also invite them to join you in the work out after the end of lesson.
Finding a more interesting and rewarding job is always an option.