It is really worth finding out, ideally from a trainer, experienced (but kindly!) friend, or by comparing video footage of yourself riding at home and in the ring, whether either you or your horse (or both) are dramatically different at competitions.
I find this applies particularly in the SJ arena: sometimes the horse can be a lot buzzier, or the rider might go for longer distances, for example.
Once you realise there’s a difference you can then have a strategy to cope with it, work on lessening it, etc, whereas if you are caught up in the moment you might not even realise there’s a difference!
Pic by Katie Mortimore.