I think you're being too hard on yourself.
Yes there are things we could have done to prevent falling off... if I had better balance for one, I most probably would have been able to stay on Honey and calm her down. Instead I fell... but at least now I know what I need more work on.
Sometimes our horses spook at things we wouldn't expect them too... my "idiot" of a gelding (I label him that affectionately lol) doesn't spook at the normal stuff... instead he recently was on a road ride and had train tracks to cross, new places to go and he spooked at a blimming letterbox that had mail sticking out of it. I'm not sure any of us could be completely prepared to react if our horse spooks at something we are even thinking of.
Don't over analyse... if he's not sore and he's spooked at something, you can get passed this. You don't need to hold his 'hand'... but he does need to know that you are there to help if he spooks.. and to calm down instead of going bronco.
♥ Seoul Searchin' for the Lovebug ♥