The mistake that most of us make is not finding the right exercise. If you hate going to the gym, why on earth would you sign up for one? It's a sure bet that membership will languish like so many do. Wouldn't it be better to find exercise you actually enjoy doing? With the right activity, it might not even feel like exercise at all.
Remember when you were a kid how much you liked to play? What kinds of things did you like to do? Maybe now is a good time to revisit some of those activities. I don't know a lot of ten-year olds who lift weights or go to aerobics classes. Kids don't exercise. They ride bikes. They roller skate. They run around the yard with the dog. They hula hoop. They play!
Now that I'm a grown-up, most of my favorite activities still involve wheels and helmets. Once I rediscovered the joy of bicycles and roller skates, exercise turned into something I actually want to do. Last summer I participated in my first Survival Race. How long has it been since you played in the mud?
These may not be the right activities for you, though. You'll have to discover (or re-discover!) your own toys. Maybe it's jumping rope or climbing trees, or maybe a nice game of hop scotch. It doesn't really matter, as long as you're moving your body and you enjoy it. Now go outside and play!