Dan Wieden is an advertising superstar who came up with the "just do it" motto for Nike (which, by the way, he didn't think was anything special; he says "When it actually aired, it surprised everybody involved because it apparently spoke some truth that was larger than sport or advertising").
In an interview with the Independent, he mentions the need to keep your thinking fresh: "I think it's important that if you're going to be innovative, that there's not a process for everything. Sometimes it seems that if you're never lost you're never going to wind up anyplace new. It's only if you're willing to be completely fucked-up that you're going to do anything important."
Illustrating this principle is a mannequin in the foyer of the London offices of Wieden & Kennedy: he wears a pinstripe suit and traditional businessman shoes, but his head is a blender, and he carries a briefcase on which are the words, "Walk in Stupid Every Morning."
Weiden attributes his success to not compromising his creative instincts, saying, "In this business, you follow one of two masters: you either follow the muse or you follow the dollar."