Luna was REALLY bad about biting me while we were playing when I first got her, and I have an EXTREMELY low tolerance for nipping and mouthing. So I'd ALWAYS end the game and take the toy with me whenever she would accidently get me, and she learned pretty quickly to control her mouth more carefully. Now, it's rare that she will mouthe me, but she always knows immediately when she does and she backs off as if waiting for me to get up and leave.... but I don't get up and leave anymore, and she is always much more careful afterwards.