[doodhwala]

Perhaps you might not be looking at other factors.

Why were you sleep deprived? Were you involved in other tasks that kept your mood up thus fostering creativity? Was it actually that the task at hand was so enjoyable that you had already been putting extra time to get it done? Did you have deadlines?

I've noticed that you're creative when you end up putting more time and thought to any activity. You can fool yourself thinking that you are not getting ideas after sitting down for just 5 minutes to do a task. But if you are deliberate in your efforts (possibly due to the kind of work or imminent deadlines), then ideas will come to your mind.