I have always thought that "good design starts with clean hands". But I have heard great designers talk about how good it is to get your hands dirty. My thought is very literal, and the latter, probably a figure of speech. So, you can take both. Get the hands of your mind dirty, but the hands on your body should stay clean in order to execute the best work you can.
Another thought. I have always related design process to the practice of folding origami. If your first fold isn't accurate, then every subsequent fold will be increasingly inaccurate -- exponentially inaccurate, in fact -- though I haven't gone through the equations to prove that theory. Similarly with any design, if you aren't collected and decisive with every step, the ultimate outcome will be sloppy and disheartening. And I don't just mean with visual execution but with the thoughts in the design process itself.
So you can make the design-equivalent of this.