Exercising can be thrilling in itself when you get yourself into the "zone". Unfortunately, getting into the zone doesn't happen at the snap of the finger. It takes a lot of warm-up. Sometimes people get discouraged because after some warm-up, they still don't experience the joy of exercising.
I find that having a routine is useful. By having a set of things to complete each day, you do not stop exercising too soon for you to get into the "zone".