At some point, I think another consideration is do you work to live or live to work?

Also, would it be an option for you to try pursuing a part-time job in fitness? Just to test the waters? You may find that teaching a class or doing personal training "on the side" may be enough spark that passion in you again.

Even though my day job can be tedious and frustrating, I really enjoy the job-security and benefits. I started a side-business. I was forced to because of the economy--but it was something I had always wanted to do but was too nervous to try. It's ignited passion for my career again. But a job is still a job and there are parts of if that are very stressful.

I had thought about quitting my job too and making a big career change. But I decided to try to make work work for me. I negotiated flex time and I get to work from home now. It's made a significant difference in my stress level. And I get to run and bike on my lunch breaks

Sorry, this post is kinda all over the place. This is something I've thought about a lot over the years. I could write a novel on it.