Many times!
At least on here we have the chance to read what we've written and then delete it. Real life is much worse...on too many occasions to count I've launched into a story only to realise a third of the way through that it's not only an incredibly dull story but I'm an even worse story teller. I'm then faced with the choice of battling through to the end, pretending not to notice no one gives a shit or to slowly grind to a halt mid sentence.
The other day, with Jnr, I got into a long and quite dull backstory in order to get close to the main point involving Ozzy Osbourne.
As I was just about to get to the not so thrilling point I realised Jnr would have no idea who Ozzy is and why the story was funny, rendering the whole exercise pointless.
I gave up.