Are you an optimist who thinks they can fly? Newsflash: You can't. Unless you're a chicken, but that's a whole different story.
Overestimating your abilities will get you exactly nowhere. Well, technically, it might get you somewhere, but it'll probably be in a ditch with a bunch of other overconfident optimists.
Want to know more about the pitfalls of overconfidence? Visit /mistakes/overconfident/underestimating/realism for a dose of harsh reality.
Or, if you're feeling brave, click /mistakes/overconfident/overestimating/punkrock for a blast of punk rock pessimism.
But let's be real, you'll probably just end up at /mistakes/overconfident/overestimating/optimism, where the overconfident crowd goes to wallow in their own self-importance.