These people blame one or more of - the horse, pony, the course, the ground conditions - anything but themselves - yet the truth is often simply that they haven't prepared properly for the challenge of the competition entered.
Perhaps the horse or pony isn't fit enough, hasn't been taught to confidently carry out what's expected - and remember that if the pupil hasn't learned, then the teacher hasn't taught - or perhaps the rider doesn't have the skill to ride the horse in that type or level of competition.
Quote of the season from an official at an affiliated one day event ... "If you organise a swimming competition, it is reasonable to assume that all the entrants can swim..."
The inference is clearly that not everyone who enters a competition can ride well enough and if you spend time watching at any competition, it's not long before it's obvious that there's quite a bit of truth in the observation!
Goodness knows what these riders do at home, but it's good to increasingly hear that 'bad losers' may just find their entries aren't accepted next time, so at least they can't spoil the day for other riders, their families and friends.