Burned out is not an phenomenon?

He said burned out is a clear case of you not enjoying the thing that you work anymore and shouldn't do that anymore.

People work around the clock just because they love doing, the company doing well, good progress is made.

When people not clear when things gonna go, they starting to "burnt out", that is the time that they should start something else, may require a break, but should not come back to the old things.