I think this is mostly being talked about in the context of starting a company or a side project. I can understand that you would feel that way about a day job

I think this is mostly being talked about in the context of starting a company or a side project. I can understand that you would feel that way about a day job and of course it's completely optional, but if you don't feel eager to work on a project that you've taken up your own initiative to start, then that is probably worth re-examining. You won't always feel that way, bit most of the time, at least. I'm currently working on a new product idea and I literally could not stop myself from thinking about it during my free brain cycles if I tried.