Shortly before he finally saw success, Douglas Adams was in a near miss from what would have been a fatal car crash. He records that as it was occurring he thought "oh well, it's been a good life"... but only after the incident did he think "actually, no it hasn't". A stark contrast to the obituaries when he died so suddenly aged 49.
Over the years, I have come to realise that many of the people (by which I mean famous people rather than real people I've actually met) I admire are as much known for their perceived "failure" as their successes. My bookshelves have a special section dedicated to three people in particular - see if you can work out what they have in common: Samuel Taylor Coleridge, Orson Welles and Peter Cook.
All three suffered the same fate: an initial spectacular burst of artistic and critical success followed by a long period which is generally regarded as a failure to fulfil early potential culminating in that dreadful school report approach to the obituary columns. Welles was certainly aware of this "They'll love me when I'm dead" he once said which is by way of defining a person, the same as the line about a classic novel being a book everyone wants to have read but nobody actually wants to read (I think it was Mark Twain - these sorts of quotations are usually Twain or Wilde).
Cook also commented on several occasions that having written the Mr Spiggot sketch when he was eighteen, he had never written anything as good since. Coleridge, likewise, produced the works for which he is primarily known during 1792, although he survived until 1834.
As to what went "wrong", I'd challenge the entire view. Coleridge hit the opium, Cook the bottle and Welles was seemingly addicted to being Orson Welles. None of this however means that they suddenly stopped producing anything of artistic worth or, more importantly, being interesting people to spend time with. It's only because there weren't obvious "products" for the critics to point at and coo over that their days are dismissed with a disappointed shake of the head.
Welles continued to try to make films to the end of his days but, as he put it, the "paintbox" was an expensive one (imagine if he'd had access to the kind of technology any child can get hold of nowadays). Cook, by all accounts, had an admittedly unhealthy lifestyle, but lots of people enjoyed his company - he performed to a smaller and more select audience.
Coleridge adopted middle age and the status of "man of letters". He moved in with an accomodating doctor who would look after him and proceeded to receive visitors, deliver the occasional lecture or article and generally settled down for a comfortable (but not unoccupied) boat ride for the rest of his days. It's difficult to find many comparisons for such a person these days: Peter Ustinov springs to mind. He was a famous actor of course, but he was also a playwright, film director and radio comedian. Yet nowadays he's mostly remembered as a wise and witty raconteur. How long will such a reputation last when there are so few "hits" to point to? Our media don't accord the same status to a great after dinner speech or a collection of memorable articles. Douglas Adams at the time he died had probably ceased to be a novelist and was starting to become more interesting as a man of ideas for whom novels had probably ceased to be the most useful vehicle.
Most of us have a fairly messy life, a washing machine jumble of stuff some of which happened by chance and some by design. Most of us are not a genius, even for a while. The majority of the creatures on this planet spend their time living in fear of starving or being eaten - literally in the case of animals and metaphorically in the case of many humans. The only thing I can claim as any kind of point I wish to make is that being seen as having "potential" is almost impossible to live up to, especially if the terms of judgement of "success" are set by someone else's account of your life and not your own.
Since I wrote this, I read a much more succinct way of expressing it, courtesy of some campaigners on disability issues although it has a much broader application: "Judge a fish by its ability to ride a bicycle and it will spend its whole life believing it is stupid."