That wasn't me talking: the perils of autobiographical writing
If you read creative writing books, there are usually several exhortations to plunder your own life and soul for inspiration. I agree that most characters, including the narrative voice, will have some element of the author in them - it's inevitable. I also know that I plunder small details from real life all the time - phrases or mannerisms from my family, everyday incidents at work that can be generalised, as well as observations from being abroad in the city. However, the suggestions to start with something real from your past (Recall an argument you've had and write about it from your opponent's point of view. Take one of your own memories and write it in 3rd-person) fill me with horror.
The problem with an exercise like that is, you might write something good. If the glimmer of a decent story emerges from it, you'll want to use it, and how much can you change (to make it unrecognisable to your nearest and dearest - or worse, colleagues and bare acquaintances) without spoiling it? This is particularly a danger with short stories, where one incident can make up nearly the whole thing, and if it's recognisably true, some people will of course assume the whole story is. There will then follow one of the following responses:
You didn't tell me you'd been to the V&A when you went for that job interview. (I didn't; I made that bit up. I do remember seeing a poster for it at the time)
So that's what happened to my gold pen! Return it by tomorrow morning and I won't call the police. (Nope, didn't even know it was missing. Seems I'm not the only one to have noticed you leave it lying around when your office door's unlocked)
You should be ashamed of yourself. (Maybe, but only because I have a mind that works that way; I have never actually done that, nor would I wish to)
I can't believe you could be so awful about Uncle Ken. I'll never speak to you again. (No, you see, a character with a similar job to mine said that about another character with a similar history to Uncle Ken. I don't agree with her - but you've already slammed the phone down)
Note that the above examples are themselves fictional: though I have encountered responses along some of these lines, I have never had a job interview in London or an Uncle Ken, nor do I know anyone with a gold pen. But you get the idea.
Most writers probably have at least one pivotal moment, the kind where every time you think of it you shudder, and/or breathe a sigh of relief. If they were already in the writing mindset at the time it happened, even then (or shortly afterwards) they were probably mulling over the 'what if' scenarios, and it would almost certainly provide a rich store of material for heartfelt stories - the emotions would be real because they'd still be vivid years later (given the type of event we're talking about). But if the events had that kind of resonance, would it be a sensitive issue for friends or family? Would they read the resulting tale and, recognising its source, assume that the character's point of view was that of the author? Dangerous territory, and so far, I'm too much of a coward to wade in.
Postscript: since writing this and putting it aside to use in a few weekends' time, I've read Smoke and Mirrors by Neil Gaiman. In the introduction he mentions that one of the stories in that collection (I forget which one, and the book is upstairs) is close enough to the truth that he's had to explain to a few relatives that it didn't quite happen that way. Which sort of proves my point, and reinforces my stand.