Most people have pet words that they always get confused. It’s possible that you’ve gone your entire life without realising your repeated mistake.
People have probably noticed but not said anything. Then when someone does correct you, you’re indignant (or defiant?), sure that you’re right. You must be – you’ve been using the word with confidence for years. You look it up and find that you’re wrong.
The exasperation (exacerbation?) of it all. Why didn’t you look it up earlier? Why didn’t someone tell you before? You then think of the times when you might have used it incorrectly. Did you use it in the interview for that job you didn’t get? Or in your wedding speech? How many witty Facebook rants have been met with silent scorn?