Also note that invariably when we design something that can be used by those with disabilities, we often make it better for everyone

Design is really an act of communication, which means having a deep understanding of the person with whom the designer is communicating.

Also note that invariably when we design something that can be used by those with disabilities, we often make it better for everyone

AS for all those mistakes I make - they are on purpose - to teach you how to deal with them

The designer shouldn't think of a simple dichotomy between errors and correct behavior; rather, the entire interaction should be treated as a cooperative endeavor between person and machine, one in which misconceptions can arise on either side.

And to get real work experience, you need a job, and most jobs will require you to have had either real work experience or a graduate degree.

The designer has an obligation to provide an appropriate conceptual model for the way that the device works. It doesn't have to completely accurate but it has to be sufficiently accurate that it will help in both the learning of the operation and also dealing with novel situations.