I've seen this happen to a few artists in the pony fandom too. They start out enjoying it, but it slowly eats away at them until they hit the point you describe at the end: they do it because they feel like they are required to, and it feels like a job and they're not getting paid.
About the shoes thing: for the love of your feet, keep some comfy footwear nearby! You don't need to be wearing shoe-shaped suicide while standing in line for a sub (for the love of your health, don't skip meals!), so don't feel bad for slipping your feet into something more comfortable during breaks.
Remember: Just because you can do something, that doesn't mean you should, even if you want to.