Most of the time I seriously do not want to work out!! AT ALL! But, the thing that keeps me going is that I do give myself the days off.. I don't really want to cheat on it, and I love the work out I do. I think finding a workout you enjoy is a big key to being successful with your exercising. I do TaeBo bootcamp and enjoy it a lot!!
I also think: okay, I've lost X amount of weight so far, I don't want to gain ANY OF IT back... so get your butt up and exercise!!
Also since i have horrible back problems if I take more than one day off my back will be screaming at me the whole day! So I suppose my own body motivates me well! haha
Eventually, you get a little better with it and find that it isn't as horrible as you figure.