I used to have a Joan Rivers quote on my wall that said
"Run scared... and they never catch you."
When we're in our comfort zone, our associative machinery is running in high gear and we're subject to cognitive illusions. An idea which seems true may only be 'truthy.' Ideas to which we've been frequently exposed seem clear and safe, and all other things being equal, we're inclined to like them and appreciate them. We may assume that we're the source of the idea. Daniel Kahneman says "Anything that makes it easier for the associative machinery to run smoothly will also bias beliefs."
As we come off a creative high (out of FLOW), we need to become sceptical of ourselves and our output. Although it's difficult to poke holes in our own ideas, we usually have a better sense than anyone else if we've borrowed, or cut corners, or fallen into a familiar rut.