Interesting use of the Hero's Journey to inspire you during exercise. Glad to see you've found it empowering! Personally I can't have too much going on in my head when I'm in the gym pretending to be a forklift. It's my place to unwind "The Flame and the Void" from The Wheel of Time series seems to be the most accurate representation of my mental layout when training. I tend to just funnel everything into one spot and let it be, not so much as a fuel but.. Compartmentalize it all and let me focus on the movements.
The exercises are still boring - up until a quest or a situation pops up. I'd usually be satisfied with Level IIs (which are pretty difficult, but far from impossible), but when something like "How many people will you save from the attacked village?" comes up, I can't but do my best by beating the most difficult (and most rewarding) option. It's inspiring to be a hero, even if it's all in my head. :)