Hello Abby, there are different ways to deal with stress during shows and improve your focus.
The main thing is to manage your emotions (stress) and focus (where your mind concentrates on).
To manage emotions you need to understand that your thoughts influence your emotions and your emotions influence your ability to do things:
Imagine that you mind is like a photocamera, you are the one who take pictures and you are the one who can decide what to put on focus and what to zoom on.
What you focus on become your reality!!
The fact is that YOU CAN DECIDE on what to focus on and you can decide on what you want your reality to be.
Reality has always 2 sides but if you concentrate on the weak side you will feel weak, insecure and your actions will not be 100%, instead if you concentrate on the strong side you will feel strong and sure od your abilities and your actions will be much more effective so you will be able to perform at 100% of your potential.
Start to use your mind as if you were the photographer of what is surrounding you and focus only on what is useful for you.
For example at shows instead of concentrating on the difficulties you have and on your weak points start to concentrate on what you want can do well and on your abilities.
Start to pay attention at your internal dialogue (what you tell to yourself in your mind) and ask your self if the questions you are asking are putting you in a useful emotional state for your show or not.
For example if you ask yourself things such as :
Why am I here? WHy can't I do this? WHy doesn't he listen to me? or thing as I'm not doing is right.. your mind will start to concentrate only on your PROBLEMS and your difficulties and you will feel emotionally weak.
Instead ask yourself things like:
How can I do this better? What can I improve here? What are my strong points here? this will make you concentrate on the SOLUTIONS and on your strong points.
So at shows:
1) concentrate on few thing and stay in the present
2) Become aware of what you tell to yourself and if it is not useful for that moment change it
3) Become aware of your emotions and talk to you in a way to make you feel better
4) move your focus on your strong points
5) create a mantra that you can repeat to yourself to make you feel more calm , something like "it's all ok" "I'm here to do the best I can do with what I have today",
6) Focus only on yourself and on your horse and eliminate anything else from your mind
Here are a few tips, let me know if you need more tips and suggestions.