If you haven't made it yet, you don't have imposter syndrome.
Impostor syndrome is insidious. You know what you know/are extremely fast to spot patterns others don't seem to notice, especially others of your age/experience. But you're just you, like you've always been; and you realize that at any time, someone could call you out for being just like anyone else, because how do you know how everyone else's thought process works? After all, you're just spotting patterns, accumulating data, and winging it. Little do you realize that that proficient/effective pattern-spotting is intelligence (or at least, one measure; measurement tools don't really count creativity, for example, which may be core to true genius, along with a host of other characteristics).
I'd have to disagree here. Impostor syndrome is an emotion. People overcome them in different ways. Mike's and yours suggestions are just two different solutions. The way I overcome it is by mentally preparing myself for the emotion and having a plan on how I can overcome it (ie - writing tests, working on a smaller problem, etc).