It has nothing to do with being insomniac.
It's the way we are wired. For some reason, even contrary to the quality of our mindset, we can effectively produce more during some parts of the day, and not feel much like it during others.
In his book, “On Writing”, Stephen King instructs writers to write during the same times of the day, everyday.
That way you can get your mind used to what's in the norm.
And it definitely is something inherent — you are either someone who is pretty active during nights, or days. If you are both, you are exceptional. If you are neither, you are screwed.
The point is to have a consistent habit, and it doesn't matter if you sleep late or rise early. You have to be able to harvest whatever you can from the “silence” that is usually characteristic of such odd times of the day.
Research shows you become the most productive during times that you think are the best to work.
For instance, just because great people begin their day precisely at 3.30 in the morning doesn't mean you have to too. If rising early doesn't work for you, the best way to keep your output consistent is to have your own time.
There is nothing wrong with not being able to be as consistent during the day as you are during nights.
Footnote
Originally published on quora: https://www.quora.com/profile/Anto-Rin