This not a problem I usually have. Not sure why! It has, however, happened to me that I send an email by mistake — more often, I have to say, I have a doubt just after sending the email (wrong recipient? Missing info?) that I’m very happy to be able to lay to rest with the « undo send » link that gmail offers for a few seconds. It doesn’t happen often, though.
So, maybe something similar when posting would make sense. A few seconds to hit the « whoopsie, that shouldn’t have gone out like that » button after posting.