On the flip side I am often glad that I only prepare and don't jump into coding/doing. It would take me a lot longer to figure out that it was a bad idea if I am coding and not sketching out the full thing. I have a whole blog of http://ideasfrommydreams.blogspot.com/ such ideas that upon reflection are usually not that great.

Problem with that approach is a small idea that isn't that great can evolve into something a lot better while you're working on it (esp. with casual games) - an idea that only exists on paper isn't going to do anything.