I was reading "Perfectionists are losers" on Escape from Cubicle Nation, and this bit jumped out at me.

When you sit back and wait until you are perfectly prepared for an opportunity, it passes you by. What highly productive and successful people do is spend as little time as possible at the edge of opportunities, agonizing whether or not to move forward.

Instead, they jump in with both feet and sink or swim quickly. After lots of real-world experience, they fine tune their understanding of the types of opportunities that will most likely be a success and the kinds of situations that will best utilize their talents.
So what do you think? Are the successful entrepreneurs the ones who managed to understand and act on the right opportunities, or is it just luck? How do you evaluate opportunities? How do you find them?