"The problem, however, is that HCD has developed as a limited view of design. Instead of looking at a person’s entire activity, it has primarily focused upon page-by-page analysis, screen-by-screen. As a result, sequences, interruptions, ill-defined goals — all the aspects of real activities, have been ignored. And error messages — there should not be any error messages. All messages should contain explanations and offer alternative ways of proceeding from the message itself.
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To me, error analysis is the sweet spot for improvement. Usually, designers do think of the order in which activities will be done. But they seldom think properly about what should be done when the person encounters problems, or when the situation is novel.
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One way to do this is to look at all the error messages, determine why they might arise, and redesign so that they either never appear, or if they might, that they are transformed into assistance. Not “help” which tells the person what should have been done, but “assistance” which offers the proper action and makes it so easy to proceed that the person might deliberately type incomplete information to get the guidance."