For the sake of argument, let's say you made a riding error (humor intended...). You were focused on your seat bones and not leaning forward in the canter transition and that worked great, but unfortunately, you forgot to also pay attention to your hand position. One flew up and forward (the outside one, of course) and the other landed back and down on top of your thigh.
Not surprisingly, your horse drifted off over the outside shoulder, sped up, and either landed in the wrong lead or just trotted fast while you started jamming hard on his back until you got him slowed down. There it is. A bald faced error.
The question becomes, now what? This is a most critical moment in the training of every horse and every rider because it becomes a bit of a Pavlovian situation. If you overreact right now, if you tighten your thighs and seat, lean forward, get dismayed, crumble to the walk, entirely lose your confidence, stop thinking and chase the horse into the canter anyhow, you are conditioning both you and your horse that errors are a BIG DEAL.
If 'reacting' is how you tend to react when you or your horse make a mistake, then these position faults and communication mishaps will slowly condition both of you to expect that after an error things necessarily get a lot worse. Before long every little error is followed by disproportionate tension based on the expectaion of an over reaction. Fair enough, the repetitive training worked like it always does, just not to our advantage!
I propose a new four letter word to replace the one you were likely using and that word is "oops." I would suggest you follow that word with a quick chuckle and a little smile. Oops has a wonderful way of cutting out the judgement we impose on ourselves and our horses when things go wrong. It's quick and light hearted and helps to remind us that this impossibly difficult work of coordinating ourselves and riding a magnificent and large horse will involve mistakes.
WIth a little oops, you can move on and return to your training quickly. And let that chuckle bounce right through those spots of tension and disappointment. I swear, your horse will chuckle too and then you can both oops and chuckle and smile your way towards glory.