I work all days being a single person start-up and thinking, coding, iterating. But what I have seen is I do not work all the time. I keep doing other stuff like household chores, attending to family, going out etc. In short I do very focused work in short bursts, say an hour or two in a day 2 or 3 times. I sleep as well in between if I cannot concentrate. I have found it very difficult to be doing something at a stretch. In fact I shutdown and do thinking with a notebook, fall asleep, wake up and continue thinking where I left and find sometimes interesting and easy way to solve things. Then I go and code it. I have found I cannot fit my thought process in a well-defined time boundary of morning 9 - 5 like I was expected in a day job.