or worse yet, during code review have the sudden realization that it is indefensible.

When all else - I mean google and more importantly talking with colleagues during breaks about what you're doing - to make you realize this is the point of code reviews. And it's good - after that realization you suddenly have one more known mistake under your belt which you won't make in future.

When I was young I practiced kendo. One of the things I learned then was that when a partner hits you, he's actually helping you realize your technique has a flaw. That's how you grow as a swordsman - and as a developer too.