Consider the worst case scenario. Fear is what holds back creativity. Fear is what makes you stick the paths that you know the best. When you consider the worst case scenario not only can you plan for it, but you can also convince yourself that the worst case scenario isn't bad enough that you shouldn't try.
For the ad person example: you might consider what will happen if you try to implement a creative new scheme to offer incentives for long-time advertising partners (like better placement in the layout, a full color ad for a reduced price, etc.). Perhaps the worst that could happen is that no one takes the offer, or that you lose money because of it. Come up with plans for how you might deal with these potential setbacks.
For the novel-writing example: your worst case scenario might be that no publisher or agent wants to market your novel because what they actually want is a clone of the latest YA bestseller.