A couple of years ago, I was talking to the wife of one of my best friends. (She's a friend, too, but I've known him a lot longer and I basically met her through him.) She mentioned - I forget exactly why, but it had to do with whatever we were talking about - that her sister really didn't like me.
Being the sweet, lovable guy that I am, I found that a bit surprising. So I asked her why that might be, and she told me. And I realized that the sister's dislike was totally justified, even though I'd completely forgotten the incident in question.
Some years previously, I had attended a birthday party for another friend from college. This was shortly after I'd returned to Dallas/Fort Worth, and (by the same token) shortly after my divorce.
At that party, I met the sister. We'd met before, once or twice, but only in passing. In the course of talking to her, I learned that she was recently married. Being a recently-divorced twenty-something male, I just shook my head sadly. "It'll never last," I said, and walked away.
Not my finest moment.
(As it happens, I was not only out of line but also completely wrong. She's still married. So I absolutely deserve any ill-will and/or poor opinion she might have about me.)