I hate that quote because it gets people on ideas that don't have immediate returns, might not be successful or possible, and gets people offtrack from working on low hanging fruit. My friend had a 3d printing company that got "moonshotted" by a consulting partner into to never being profitable. The hardest thing for a lot of people is not recognizing you don't need a game changing idea. A slight spin on an existing idea usually is enough.
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If you can't explain it to a six year old, you don't understand it yourself.