Most people on the thread have this correct: there is a difference between resentment and burnout. I understand this innately, as I've been there with both feelings, and they are quite different.

When I felt burned out, it was literally like a flame on a match stick. I was exhausted and didn't see a way out of the situation (amazing what a little perspective will get you.) I didn't want to do my job, because my head was full and it felt heavy to me.

Contrast that with resentment, and I was pissed off (and motivated.) I had energy to change the situation, which was entirely different from feeling burned out.

One situation gave me energy and focus; the other felt like an immovable burden. Big difference to me.