To me, error analysis is the sweet spot for improvement.

We delude ourselves if we believe that skilled behavior is easy, that it can come about without effort. We forget the years of tuning, of learning and practice it takes to be skilled at even the most fundamental of human activities: eating, walking, talking, reading, and writing. It is tempting to want instant gratification - immediate expert performance and experiential pleasure - but the truth is that this primarily occurs only after considerable amounts of accretion and tuning.

So what does a good teacher do? Create tension - but just the right amount.

It is relatively easy to design for the perfect cases, when everything goes right, or when all the information required is available in proper format

If you think the products don't match what you want from a product, don't buy it.

In my opinion, no single design is apt to be optimal for everyone.

User experience is really the whole totality. Opening the package good example. It's the total experience that matters. And that starts from when you first hear about a product experience is more based upon memory than reality. If your memory of the product is wonderful, you will excuse all sorts of incidental things.