I was thinking some more about the past that comes up to haunt you in so many ways: things you could have said but didn't think of till too late; things you didn't understand until later - forgot? But then there are major gaffes that really fester. Aldous Huxley called them floaters, I think in his novel POINT COUNTERPOINT.  A woman character remembers her floaters painfully and cannot forgive herself. I think we all have those, too, and they're the kind of thing that keeps you awake at night.  The commonest floater is the one that lies there when you have put a foot in your mouth, like asking after a person's mother and she just died a few weeks before and you should have remembered.  Or saying how much you hate rhyming verse, especially in narrative form, and your friend has just published a whole book of it as a novel. You will be able to add many examples, I'm sure, if not now, then tonight when some tactless bumble of yours floats up to torment you. They are  not innocent errors, they are things you should have known better than to say or do.  What were you thinking of?  Well, actually, you weren't thinking at all. Take comfort, if you're a writer.  Out of  your own painful experience you can create a scene in which your protagonist can be mightily embarrassed. Audiences will love it. Does that help? 

Hey, I just looked up gaffe in the dictionary and there are some lovely synonyms you can writhe with: blundermistakeerrorslipfaux pas,indiscretionimproprietymiscalculationgaucheriesolecisminformal slip-uphowlerboo-boofluffflubbloopergoof.