It's not necessarily the meaninglessness of work. I had one project at a former employer I became emotionally attached to and worked for some weeks from 6am to

It's not necessarily the meaninglessness of work. I had one project at a former employer I became emotionally attached to and worked for some weeks from 6am to 6pm on it. After figuring out the project would not be finished any time soon though I almost couldn't work on it anymore after a holiday. It was like running sprint after sprint and realising you need to run at least a marathon. I did not have a real burnout but I think I was very close.