When you are playing a game and feel like you are about to loose, just
exit the game. When you are asked if you want to save the game, click 
Yes. If you are warned that an already saved game exists, and asked if
you want to replace it, click Yes. Then start the game again and look 
at the statistics. The game you just lost was not taken into account! 
Now you can keep a clean record with 100% wins!