In the beginning there was a cat...

Lesson #1: No writing is ever wasted.  Even if it's just a stepping stone to the next idea - you couldn't reach the next idea without it.

I don't know about you, but my best ideas come to me just as I'm falling asleep.  Not great if, like me, you've got someone lying in the bed next to you, who really doesn't want their eyeballs burnt out of their sockets by the bedside lamp.