If you actually give the pieces places in life it can become a bit more clear as to what I am talking about. The pawns would represent the people in life that we use to our advantage. The queen would represent a close loved one that keeps our sanity in check. The king would represent our sanity. The knight would represent the people who fight for us to protect themselves and you. The bishops would represent the people who will always stick by our side. The rooks represent the people who are logical and only move in one solid direction. The opponent represents insanity trying to consume us or our temptations trying to get the better of us. This is why the pieces look exactly the same except for color, which should represent the difference in minds.
The whole battle itself is showing the struggle that goes on in our heads while we are finding our temptations in real life. Which is why you will notice, when you play chess you are using your brain to win almost the entire time. The way you lose a piece in the game is if your enemy gets you into a position in which they can capture you or eat you. The game never makes it clear that your piece dies after it is used, you just assume that. But actually the piece has been overcome by insanity, so much so the piece might as well be dead to you.
When you battle insanity in real life, you tend to drag people into your battle. Of course we would also need the definition of insanity in order to understand this. Insanity means someone who doesn't fit in to society. If we stray to far away from the comforts of our mind we tend to wander, and sometimes we wander a bit to far and we find ourselves at the gates of insanity. Then suddenly that gate slams shut and you realize all too late that its " Checkmate".