If he turns around and leaves when he is supposed to do something, you should walk to another side of the paddock/stable and wait for him
Horses learn to do what works for them & quit doing what doesn't work. Simple as that. If the horse walks away from you because he doesn't want to be with you/do something, and you allow that to work for him - you quit asking, take any pressure off & remove yourself - you are teaching him
that he is 'right' to just leave whenever he doesn't want to 'play your games'.
I can see though, that it could
work, under certain conditions. IF
this always works for you horsegirl, when you walk away the horse immediately comes back to you, I think you're not understanding the whole situation & discounting some of the important factors. Number one factor is that a horse that does that DOES want to stick to their human, for whatever reason. Perhaps they've been 'corrected' whenever they're not close(like 'horse whisperers' such as MR teach). Perhaps they're lonely or insecure or bored in their environment. Perhaps they have associated being close to the human with Good Stuff...