Companies fail because of it. It usually takes desperation, a neglectful boss, or a lapse into mania to happen at all. I suggest it could be the natural course of wise design. The best way to learn how to do something really right is to do it wrong while doing your best. The more complex a project, and the deeper the unknowns, the better the chance that hindsight and horizontal thinking will turn up significant opportunities.
Good design is transparent.
Your site's usability will never be great and fluid, it will never disappear, recede into the cozy subconscience until you thoroughly grasp the sphere of issues. The best way to get to that kind of mastery is to work through the whole subject. Thinking and talking and waving hands only goes so deep. Getting something to work pushes your mind into all kinds of important nooks and crannies that you couldn't begin to anticipate. The last thing one discovers in composing a work is what to put first.