I'm glad you explained what your "arena" was…my first thought was why don't you simply close the arena gate so he can't leave the arena! LOL! At any rate… in my opinion, if he's doing the same thing over and over, all you are doing is reinforcing that behavior by allowing it to continue. Personally, I'd do what mom2 pride suggests as well as doing more transitions. And, if I'm understanding you correctly, he has no idea that he has to stay within the tilled area - you have no rails/barrier/fence to use as a guide to help him understand or work off of. I'm not sure what you mean by "he tries to pull all kinds of tricks" - but reading this makes me wonder if you are not over doing something to the point that he is "running out" in frustration and/or confusion rather than out and out disobedience.