As a child, I excelled at every subject in school. Scored in the 99th percentile on all standardised tests. And, I always placed into the school spelling bee. Often won. In sixth grade, I failed on a fairly difficult word. I was irritated enough that I didn’t bother to remember what word it was.
A year later, in seventh grade, I was given “unnecessary”. And failed. And in that exact moment remembered that I had failed on “necessary” the year before.
Never forgot how to spell it.