I think one needs to distinguish between being a workaholic for some corporation and doing it because you're starting a company or working for yourself.

The former is obviously going to be painful and the latter might not even feel that much like work.

Maybe I'm just justifying because I'm definitely a workaholic, and I'm in the second scenario and it feels totally sustainable. The first scenario I also did, and it was hell, I wouldn't do it again. It was a necessary evil to get the financial security to start my business (self angel funding - no permission required, no strings attached.)