It doesn't have to be this way. The best way to stick with an exercise is to find one that you enjoy. For some people that's lifting weights, or running distances. Others like biking or yoga. I play ultimate frisbee, which I find to be a lot of fun and a great exercise. I'll be the first to admit that I should do more, but chasing a piece of plastic through the air for two hours a week is a whole lot better than sitting down at home. Try seeing what sports leagues are in your area, maybe you'll find something you like.