My corgi Einstein refuses to stop playing, even if he is too exhausted to play! Even after we take him running at the dog park every day he still wants to try and play when we get home. When he finally calms down his little heart is beating so fast and his little body is just shaking because he's breathing so hard. Is this normal? Should we stop playing with him when we think he's tired? Because he won't stop until he just falls over.