In 1956, Pablo Picasso was filmed painting a number of pictures by French director Henri-Georges Clouzot. Canvases were filmed from behind, so you don't see the hand or brush of the artists...just the marks appearing. Watching the master at work is mesmerizing. The most astonishing thing is how much Picasso worked and reworked every image. Sometimes obliterating beautiful, seemingly fully realized compositions, painting over them, and building up layer upon layer.
This way of creating correlates with the techniques of many great authors, whereby they write and rewrite and rewrite til perfection. Hemingway once said "The first draft of anything is shit." This is a healthy mindset to have when composing anything from a novel to a song or even ad copy. Advertising legend David Ogilvy emphatically recommended, " Never send a letter or a memo on the day you write it. Read it aloud the next morning — and then edit it."
I think being an inherent skeptic is a benefit when working in a creative profession. Certainly the second part of the two-step process of idea generation–idea evaluation gains from always entertaining the notion that an idea can be improved. The trick of all artistic endeavors is knowing when a piece is as done as it needs to be.