How to balance my own fitness and instructing fitness classes?

I'm a group fitness instructor that teaches Step/strength training two days a week and a Zumba class one day a week. I'm a bit on the cubby side and I really want to get in better shape. I really want to try the P90X and/or Insanity. I also want to be able to balance my own fitness routine while still teaching classes and not over due it or injure myself. Do you have any suggestions?