Between awake and asleep

There is a state between being fully awake and being asleep that kicks my brain into overdrive. It happens at night when I'm in bed but haven't fallen asleep yet or first thing in the morning when I've just woken up. If I'm thinking about a story at that time, I'll come up with lots of great ideas for it. If I'm thinking about work (which is more often the case), it helps me figure out what I need to do for the projects I'm working on.

What is it about this state of mind that fuels creativity?...