Mistakes in a World of Gradients

I've been working on material for avoiding software mistakes, and have been searching for clarity on how to actually define "mistake."

I've been struggling with common definitions that are very black and white about what is wrong and considered "an error" or "incorrect".  Reality often seems more of a gradient than that, and likewise avoiding mistakes should maybe be more a matter of avoiding poor decisions in favor of better ones?

I like this definition better, because it accounts for the gradient in outcome, without missing the point.

"A human action that produces an incorrect or inadequate result. Note: The fault tolerance discipline distinguishes between the human action (a mistake), its manifestation (a hardware or software fault), the result of the fault (a failure), and the amount by which the result is incorrect (the error)."

 GE Russell & Associates Glossary - http://www.ge-russell.com/ref_swe_glossary_m.htm