Failure to finish.  I've had, to date, 7 ideas that, had I finished executing, I would have been first to market (in most cases, by years).  I would have been beaten to market on one other product, and really close to tied with another few.<p>In imaginary-land, where I live, of the 7 companies I beat to market, 4 of them had million dollar + exits or acquisitions, so I COULD have been worth 45-55 million, give or take.<p>My number one challenge in doing anything is not having somebody else to motivate me, or even just tell me what to do.  With almost everything I do, I solve the challenges first; the bits that otherwise make the product, or the bits that aren't obviously going to work... once I've built those out, the project is mentally done for me.<p>I will often fail to do the little things, the EASY things even, like building the change password page, or sending an email for account creation, etc.  I'm so bad at it, even, that I will often stop after I have figured out HOW to solve the problems, without ever even bothering to actually implement.<p>So yeah, that's why I'm stuck with my 9-to-5.  Good question.