If you ride a tense of stressy horse it can be difficult to understand how you can influence him other than hanging on for the ride and pushing forward.
However there are some things you can do with your own body that will help a little-or at least not make it worse!
It seems obvious but it can be really tricky to actually do, but try it to hold tension in your own body.
Start with your breathing. Breathing into your Diaphragm or belly breathing taps into your Vagus Nerve which creates relaxation in your own body that will transfer to your horse. It also encourages relaxation of your Psoas muscle that sits at the front of your hip, this will allow your seat and leg position to be more relaxed.
Keeping your elbows closed into your sides encourages you to switch on your back muscles which will allow your arms and hands to relax down the reins. You will have a much more stable but relaxed contact if it comes from your back rather than your arms.
Before you get on rolling your glutes on a small ball can release tension in your seat, and of course some general movements such as arms swings or fig 8s, leg swings, squats and lunges can encourage muscles to switch on and work more efficiently rather than bracing under tension.
If all else fails have a little sing song as it will help you do the above without even realising! I’d avoid any Mariah Carey high notes though……..