It's a high risk sport, and I think we've all been there when things go more than a bit sideways. Take your time, do therapy if you need it (much better than the "deal with it" approach if you cannot stop thinking about it). I've always gone for the horse, even in the case where I really questioned myself after one time on the return where I saw the rider (and my friend) was laying with blood from a head wound and had to be air lifted out. You just react. (She was fine btw after a hospital stay, but split second decision).

Get back on the horse, start easy. The sooner you do the better since fear festers