Your users are never stupid. Sure, there are many users who may not be experts in using your application (or web site, or remote control, or door knob) – in fact, most users of your interface won’t be experts at using your interface. Even if your product is Photoshop and your users spend half their day inside your app, that means they spend half their day inside another app where they are taught all kinds of unsavoury habits.

It’s never your user’s fault. If one user gets stuck somewhere, you can bet your farm that others will face the same problem. Never accept “I’ve just been stupid” as an explanation for user failure. There’s always something you can do to fix usability issues.

Nothing to add here – check it out, pretty good blog. (Yeah, I know this post sounds like link spam. Which in a way it is. But I love the quote, because it really resonates with a feeling I always had.)