I think you're right, and your purpose -- being increasingly happy, confident, and holding yourself in high esteem -- those are all ingredients that would consistently support motivation for any goal, including fitness.
The intention I hold for my workouts is Being Strong; that's what inspires me to push through for a breakthrough and to go to the gym when I don't feel like it. I look for evidence of being strong and I nurture it -- like celebrating being able to carry all my groceries, or having endurance in sex or on a long walk or bike ride.
Thanks to you guys I'm going to see how I can see my workouts in terms of my Purpose: To boldly generate and facilitate free-flowing love and joy -- in way that inspires me. Or maybe I'll end up revising my purpose!