Your horse requires 100% of your attention if you expect his. Some methods rely on the horse having to pay attention, regardless of if we are or not. This doesn't seem fair to me. If a student is in a class room and the teacher is off in La La land. That class is going to find other ways to entertain themselves good or bad. They are also going to resent and not respect that teacher too much.
If you and your horse are completely focused on each other as much of the time as possible, the communication should be more effortless and as a result you should pick up on subtle cues that your horse may be getting nervous about something. Then you can take measures to prevent a spook or redirect your horses energy somewhere else.
I feel that a lot of accidents are a result of lack of focus and awareness in the horse and rider.
So try this exercise if you feel you have an unfocused or spooky horse. Take measure to make yourself feel safe, and spend a whole session completely focused on what your are doing and who you are doing it with. Let me know how it goes in the comments section!