Happened to me once
I didn't realize it at the time, but I had a job that did this to me. They kept increasing my work load. When I finally broke and said "This is too much" I was told "We'll deal with it and see what can be done"
Things were OK for about 2 weeks, then it started all over again... only now it was "Your the best we have, you HAVE to take this, no one else will take it!".
Anyway, in the end, I broke, I burned out and walked away from the employer mid work day. I walked into my bosses office, said "I'm fucking done with this job, here!" handed in my laptop and phone and walked away, without a single word and went home. I spent the next 3 months healing and trying to cope with what happened. It wasn't until I got a new job that I realized it was the job, not me... with a new employer I fell right back into IT and loved it again!
I was fortunate in the way that I had established a solid reputation as a tech and a few months later a few of my old "Contract" companies called me to offer me a job.
The take away for me, I now know my personal warning signs of burning out, and I am able to better identify bad employers. In the end, we have to stand up for ourselves.