The first step of writing an error message is to not tell the person, and figure it out yourself.
What can you add to make a boring task more interesting?
Sound
Information
Movement
Color
Repetition
People make mistakes all the time.
What kind of performance mistakes do people make?
Commission errors
Omission errors
Wrong-action errors
All of the above
People use different techniques when they realize they've made a mistake. The 3 main error strategies are 1) Exploration, 2) Exploration, and 3) Exploration.