I'm always on time for appointments and scheduled events, but for a while, I would allow myself to skip exercise. So, now I make an appointment, and schedule myself a time to do what I need to do! A planned activity and time can be much more effective than a "I'll do some exercise today" vision.
The SparkPeople planner is handy if you're near your computer - you can get an email reminder. And you even get a spark point when you make an appointment. Win/win!