That’s a really quick way to discourage your horse from even wanting to try, to make him afraid to make mistakes. Instead, reward each try. Ask for a little more each time, but acknowledge every try. Some horses will try absolutely everything before they hit on what it is you’re actually asking them to do. Never, ever punish that willingness to try, because that will absolutely make your horse miserable and he will eventually stop trying. Then he’ll come to me for “training”, when all he needed in the first place was a little encouragement. Don’t be stingy with praise. Don’t praise the wrong responses or behaviors, but allow yourself to be a little effusive with praising the right responses.
If you are having a “bad” ride, and are at total odds with your horse, give up your agenda, do something you know your horse is good at, and then make sure you quit when he’s doing something good. I’ve had rides where all the horse could do that day without it turning into a fight was walk and halt. So, I had to abandon what I thought he *should* be able to do and we walked and halted until I could tell him what a good boy he was and quit on a positive note. It’s worth doing, because we all have bad days. Quite often the next day you will have the best ride ever, just because you didn’t pick a fight and put your relationship with your horse above your agenda.
Along these lines, if your horse is doing a particular exercise really well, and he does it three or four times in a row, stop before he fails out of fatigue. Don’t try for 5 or 6 times and risk him not being able to do it perfectly that 5th or 6th time. One of my trainers always says, “Do it three times to prove it wasn’t a fluke the first two.” But, don’t push your luck. If he feels successful and that is the memory he brings into the next ride, your horse is more likely to give you his best effort the next day.