I hope you have had success with the method I laid out in the last lesson. I realized that I forgot to mention why a horse might be doing this, and how to get over that main problem, instead of just dealing with the symptoms.
If you use a curb bit (one with leverage – it does not matter if it is jointed. If it has shanks on the side it is a curb bit and it is severe) there is a greater chance that your horse will have issues, unless you are a very good rider. A curb bit is designed to be used to refine complicated movements on horseback, and it is certainly not meant to be used by beginners simply because they need more control over their horse. If you need more control, your horse, or you, needs more training! Any well trained horse should be able to do whatever you ask of it calmly and willingly in a plain jointed snaffle bit. So, please avoid a curb bit if at all possible. One slip-up and your horse may have his mouth permanently damaged, leaving him ill disposed to take the bit nicely the next time you want to ride him. I mean, if someone stuffed a lump of metal in your mouth and it hurt, you would do everything in your power to keep that same metal out of your mouth the next day! Remember that a horse is a living creature with nerves, just like us. In fact, in many cases, horses are way more sensitive than we are. Treat him as such and be as gentle as possible. A horse with a ‘hard’ mouth has simply been desensitized to the action of the bit, and this takes a long time to fix. It is not impossible, however! Virtually any problem a horse has can be remedied with time and proper training techniques.