Yep. Just happened recently.
About the best you can do is acknowledge the mistake, try to learn from it, and not repeat it again.
When it comes to people, mistakes are harder to acknowledge and analyse. It's far easier ego-wise to always blame them for the problem. Push them away. Refuse to figure out what you did wrong and refuse to work on not repeating that mistake.
That said, it's also difficult to know what "normal" people are these days. Is it all the people who take antidepressant drugs? Is it the people who go out and get stinking drunk over the weekend? Is it the silent, invisible people that you never actually see because they're busy doing their thing?
So when you make a mistake, the question can also become: Was it my mistake, or are they really that fucked up?
In this case I cannot really tell.
Which makes it hard to not overanalyse and overthink things.
Chances are high, knowing what I know of this person, that they are actually the problem. After all, NPD and BPD people make it a pattern to always push their problems on to you. To blame you for the situation at all times, it's never their fault.
This one does show some signs of BPD.
I guess that I will find out with time. Abusers love to be able to drag you back and abuse you some more. If this one tries that: then I'll know that it isn't me who has a problem. My mistake will have been getting even peripherally-involved with someone who is a very-well-hidden nutjob.
At any rate: define normal. I know that I am nowhere near normal.
Definitely semi-ghost time.