Admitting that you're wrong may sound like a bruise to your ego, but only if you feel personally tied to the project. Pixar has a good approach; they vehemently emphasise that the project is always separate and thus criticism towards it are never personal. If you try and do it for your own project, you can get a more objective view and explore much more design possibilities.

The downside to this is a longer process, and actually you become more prone to "analysis-paralysis". But still I would argue that it's part of developing yourself to become more objective, at least that's the experience with my project anyway. It's funny that we're taking about this because two weeks ago I had to tear down an entire product architecture, built over 3 years, to start all over again. I had made one flawed assumption at the beginning, and it got buried so deep that I didn't realise for a long time. It manifested itself into a set of problems that I kept hitting into, until I had to concede that there's something rotten at its core.

It sounds like a waste, but no: the new product was actually designed at a much shorter time, and far better than its predecessor (well you'll just have to take my word for now ;)) And yes I do feel a bit silly for being in denial before.