Im all for making it fun and enjoyable for the horse, but there needs to be a point when we are NOT playing anymore. I had a mare try to push me at the hitching post once (owner was a parelli worshiper). I pushed the horse back and ignored her. This horse had NEVER been told no, or what to do. She pushed me harder and I smacked her nose, I don't care whos horse it is, my space is mine and I don't want teeth that close to me (especially teeth belonging to a rude and mouthy horse) thank you. Oh that mare was pissed. I thought she was going to charge at me over the hitching post. I got irritated with her and just left, not my horse not my problem, and if the owner is just going to sit there and "porcupine" the mare for "being sassy" I don't need to continue the conversation.
I play games with my mare when I introduce something new, but once she gets it its no longer a game. I want her to not be bored out of her mind but I also know that my smart lil arab will try to out think me with games. When I say do it, she needs to, especially if she has done it over 100 times before. She is smart and I found out the hard way that there needs to be a time when "Play time" is over.
I will have to admit I don't like parelli because I have seen too many people hurt fallowing the method (and many bratty horses). So take my info with a grain of salt.