That is not really related to this thread since this is about how to "start a company with no free time" (hint: there is no such thing as "no free time"), but to answer your question, I did reach my goal and went above and beyond.
Yeah, i'm not advocating that you do this until you burn out or die. I think the most important part is that I would sometimes just stop working when I don't feel like it. And don't do anything, or sleep for 12 hours, or whatever. Then soon enough I will want to come back.