"I would think that passion is the least predictive part of success....[The most important part] is probably some combination of luck, I would say is the number one thing, but you've got to be prepared with some amount of talent, and picking the right field, and staying in the game long enough that luck can find you. That's mostly what I write about; how to prepare so that you're ready when luck finds you."
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Related book: How to Fail at Almost Everything and Still Win Big: Kind of the Story of My Life - by Scott Adams